JP2010085384A - Range switching circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a range switching circuit of a small measuring error caused by leaking current of a diode switch used in a current/voltage conversion circuit or offset voltage or bias current of an operational amplifier, a buffer amplifier, or the like, and to provide a circuit for reducing spike noise during range switching. <P>SOLUTION: In the current/voltage conversion circuit in which the range can be switched, reverse bias voltage is applied to the diode switch constituting the range switching circuit to reduce measuring error caused by the leaking current, a buffer amplifier is put out of a current path to reduce measuring error caused by the bias current, and a voltage-controlled resistor makes resistance variation of a switch used for range switching become a speed traceable by response of a negative feedback circuit to reduce the spike noise. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a current / voltage conversion circuit that combines a range switching circuit that reduces a measurement error caused by a leakage current of a diode switch, a bias current or an offset voltage of a buffer amplifier or an operational amplifier, and a plurality of range switching circuits. And spike noise reduction at the time of circuit switching in the negative feedback circuit.

  When measuring a physical quantity such as the magnitude of current or the amount of electricity or power related to the current, an I / V conversion resistor is used to convert the current into a voltage. Conventionally, several types of I / V conversion resistors having different resistance values depending on the magnitude of the target current are measured by switching with a switch, a relay, or a semiconductor switch. This is generally called range switching.

  In general, it is difficult to switch the range of a current that has a large dynamic range and changes at high speed, but it has been realized by the methods disclosed in Patent Document 1 and Patent Document 2.

FIG. 40 is a configuration diagram of a typical current / voltage conversion circuit disclosed in Patent Document 1 when the number of ranges is three. Ranges 1, 2, and 3 are set from the small current range, respectively. Range 1 is the minimum range.
I / V conversion resistors 3, 4, and 5 are for ranges 1, 2, and 3, respectively, and resistance values are R1, R2, and R3, which are connected in series, and current bypasses are provided to I / V conversion resistors other than range 1 Provide a circuit.
The current bypass circuit of the range 2 is switched to the terminal voltage on the I / V conversion resistor 4 side of the diode switch 6 when the drive signal of the current drive circuit 92 which is the output unit is turned off by the switch 91 in the range switching circuit 90. In some cases, the voltage is switched to the voltage output V1 side of the operational amplifier 1 as an error amplifier via the dead zone circuit 93, and the current drive circuit 92 drives the I / V conversion resistors 4 and 5 via the diode switch 6.
The same applies to range 3. Details of the operation are described in Patent Document 1.
Hereinafter, this is referred to as “resistance series current / voltage conversion circuit 1”.

FIG. 41 is a configuration diagram of the main current / voltage conversion circuit disclosed in Patent Document 2 when the number of ranges is three.
The I / V conversion resistors 3, 4 and 5 of each range are connected in series, and a current bypass circuit is provided for each I / V conversion resistor other than the minimum range.
The range 2 current bypass circuit converts the drive signal of the current drive circuit 104 in the range switching circuit 100 to the terminal voltage of the diode switch 6 on the I / V conversion resistor 4 side via the limit circuit 102 by the adder 103 and the dead band circuit 101. The I / V conversion resistors 4 and 5 are driven by the current drive circuit 104 via the diode switch 6 and the operation is performed for automatic range switching. It is to become.
The same applies to the current bypass circuit of range 3. Details of the operation are described in Patent Document 2.
Hereinafter, this is referred to as “resistance series current / voltage conversion circuit 2”.

49 shows the input / output relationship of the dead band circuit, and FIGS. 50 and 51 are examples of known dead band circuits.
For the following explanation, the dead zone circuit when the absolute value of the dead zone set voltage is the same value is defined by the following equation.
Vout = db (Vin, Edb) (1)
Where Vin is the input voltage, Edb is the dead band setting voltage, Vout is the dead band output voltage,
When Vin <-Edb Vout = Vin + Edb
When −Edb ≦ Vin <+ Edb, Vout = 0
When + Edb ≦ Vin, Vout = Vin−Edb
And

The resistor series current / voltage conversion circuit 1 and the resistor series current / voltage conversion circuit 2 are summarized as follows. When the range is off, both ends of the diode switch are set to the same potential to eliminate the leakage current, and when the range is on, the output signal of the operational amplifier is used. The current bypass circuit is driven, and FIG. 42 is a configuration diagram in which the current bypass circuit is collectively expressed when the number of ranges is two.
Hereinafter, this is referred to as a “resistance series current / voltage conversion circuit”.

  Since it is disclosed in Patent Document 1 and Patent Document 2 that it can be easily expanded to more than 3 ranges by adding the same range switching circuit as in the case of 2 ranges, for clarity of explanation. In this document, the number of ranges is set to 2 or 3 except when necessary, the minimum range is set to range 1, range 2, and range 3, and the full-scale current values are set to I1FS, I2FS, and I3FS, respectively.

  In a region where the operational amplifier 1 as an error amplifier subjected to negative feedback operates linearly, as shown in FIG. 42, when the non-inverting input terminal is connected to the ground (circuit operation reference potential), the potential of the inverting input terminal is the input current I. Since the output voltage V1 is controlled so as to be always equal to the non-inverting input terminal potential regardless of the magnitude of the current input terminal voltage e, the current input terminal voltage e becomes substantially 0V. Hereinafter, in this document, e is treated as 0V for the sake of clarity.

  It is assumed that the resistance values of the I / V conversion resistors 3 and 4 for converting current into voltage are R1 and R2, respectively, the magnitudes thereof are R1> R2, R1 corresponds to the range 1, and R2 corresponds to the range 2.

The range switching circuit 80 drives a bypass circuit when the range 2 is on.
In this document, the direction of the bypass current is defined as a current discharge direction when traveling from the current drive circuit to the I / V conversion resistor, and a current suction direction when traveling from the I / V conversion resistor to the current drive circuit.

The range controller 81 generates a voltage output V21 like the graph of I-V21 shown in FIG. 42 from the output voltage V1 of the operational amplifier 1 and the lower end voltage V2 of R2.
The buffer amplifier 10 buffers the lower end voltage V2 of R2, and is provided as necessary.

The outline of the circuit operation of FIG. 42 is as follows.
The arithmetic circuit 2 performs A / D conversion of voltage signals, current calculation, range on / off control signal control, etc., and functions by combining hardware such as an operational amplifier, a differential amplifier, a comparator, and an A / D converter. There are many different implementation methods using known techniques such as realization of functions or a combination of these and a microcomputer system to realize functions by hardware and software. However, in the present invention, if necessary functions can be obtained, Since the method does not matter, it is indicated by an arithmetic circuit as a generic name. For the differential amplifier and hardware differential amplifier, the data after A / D conversion may be subtracted by software to obtain the difference.

  When the input current I is less than I1FS, the arithmetic circuit 2 turns off the range 2 on / off control signal, and the range control unit 81 sets the output voltage V21 of the current drive circuit 82 to the same value as the voltage V2 at the lower end of R2, so that the diode The potential difference between both ends of the switch 6 is 0V, and the diode switch is turned off and no current flows, so the current I21 becomes 0A.

Accordingly, the input current I flows through R1 and R2, and I = I1, and the arithmetic circuit 2 measures the voltage V1 at the lower end of R1,
I = V1 / (R1 + R2) (2)
The value of the input current I is obtained by the following calculation.

When the input current I exceeds I1FS, the arithmetic circuit 2 turns on the range 2 on / off control signal, and the operational amplifier 1
I = I1 + I21 (3)
The output voltage V1 is increased or decreased so that the output voltage of the current drive circuit 82 increases or decreases accordingly, the diode switch 6 is turned on, and the bypass current I21 is driven.
The arithmetic circuit 2 measures the voltage V2 at the lower end of R2 at that time,
I = V2 / R2 (4)
The value of the input current I is obtained by the following calculation.

  As described above, the diode switch 6 functions as a current on / off switch between the current drive circuit 82 and the lower end of R2. Here, the current drive circuit 82 is not a simple on / off switch operation, but has a major feature in that it operates as an amplifier having a broken input / output relationship. The analog switch cannot be turned on / off relatively. This is particularly advantageous when measuring a large current by switching the range.

FIG. 60 shows an example of voltage-current characteristics of a general diode. When the forward voltage VF is several hundred mV or less, the current is almost 0 A, and when the forward voltage VF is more than that, the current increases rapidly. Turns on.
FIG. 61 shows an example of the voltage-current characteristics of a diode switch connected in parallel in both directions. The switch characteristics in FIG. 60 are such that VF and I are bidirectional in positive and negative directions.
The diode switch of the resistance series current / voltage conversion circuit shown in FIG. 42 uses the characteristic that both ends thereof are equipotential and the current becomes 0 A when the voltage between both terminals of the diode is around 0 V as shown in FIG. A general current / voltage conversion circuit has a sufficient switching function.

  However, the peripheral circuits of the diode switch 6 such as the operational amplifier 1, the range switching circuit 80, and the buffer amplifier 10 have an offset voltage and a gain error. Even if an offset adjustment circuit and a gain adjustment circuit are provided for these, the ambient temperature condition is included. Therefore, it is difficult to make the forward voltage between both terminals of the diode switch completely 0V.

  When these diode switch peripheral circuits are not provided with an offset / gain adjustment circuit, the forward voltage between both terminals of the diode switch may exceed several mV or 10 mV, and a minute leakage current flows in the forward direction. When measuring a minute current such as a picoampere level, there is a drawback that it may cause a measurement error.

  In FIG. 42, when the number of ranges increases, if there is no buffer amplifier or buffer amplifier equivalent to the buffer amplifier 10, the connection point between the input current path and the arithmetic circuit 2 increases, and these bias currents are added to the input current to be measured. Therefore, when measuring a minute current, there is a drawback that it causes a measurement error.

  FIG. 40 is a block diagram of a typical current / voltage conversion circuit disclosed in Patent Document 1 called the resistance series current / voltage conversion circuit 1 when the number of ranges is 3, but switches 91 and 91A. The dead-band circuits 93 and 93A are provided in the outputs of the operational amplifier 1 and the current drive circuits 92 and 92A driven by the fact that the response of the negative feedback circuit cannot follow when the signal is turned on / off. However, there was a drawback that a relatively large spike noise was generated.

Similarly, in the negative feedback circuit using the general operational amplifier circuit as shown in FIGS. 53 to 58, there is a problem that spike noise occurs due to the fact that the response of the negative feedback circuit at the time of switching the circuit by the switch cannot follow. . Since these circuits are basic circuits that are very generally known, detailed description of the operation is omitted.
The operational amplifier circuit here may be either an integrated single operational amplifier or an operational amplifier circuit configured by combining a plurality of electronic components.

53 shows a known inverting amplifier circuit using negative feedback, where 301 is an operational amplifier, 304 is a resistor having a resistance value R11, 305 is a resistor having a resistance value R12, 306 is a resistor having a resistance value R2, and 302 is an operational amplifier. Is the load.
310 and 311 are switches, and transistors, FETs, analog switches, mechanical relays, and the like can be used.
In FIG. 53, the input resistors R11 and R12 are switched by the switches 310 and 311 to change the amplification degree. When the switch is turned on / off, the input resistance value of the negative feedback circuit changes suddenly, but the response of the negative feedback circuit follows. In general, there is a problem that spike noise occurs in the output of the operational amplifier 301.

  FIG. 54 shows a known inverting amplifier circuit using negative feedback, and the negative feedback resistors R21 and R22 are switched by switches 310 and 311 to change the amplification degree. When the switch is turned on / off as in FIG. There is a general problem that spike noise occurs in the output of the operational amplifier 301 because the response of the negative feedback circuit cannot follow the change in the negative feedback resistance value.

FIG. 55 is a known constant voltage / constant current generation circuit using negative feedback, and switches between negative feedback resistors R21 and R22 with switches 310 and 311 to select whether to generate constant voltage or constant current. As in FIG. 53, there is a general problem that spike noise occurs in the output of the operational amplifier 301 when the switch is turned on / off.
For example, Patent Document 3 discloses a method for avoiding spike noise when switching a control signal and a negative feedback signal as shown in FIG. 55 in a negative feedback circuit, but requires a relatively complicated circuit and operation procedure.

  FIG. 56 shows a known constant current generation circuit using negative feedback, and the current detection gain is selected by selecting whether the both ends of the current detection resistors 306 and 307 are short-circuited / non-short-circuited by the switch 310. Similarly to the above, there is a general problem that spike noise occurs in the output of the operational amplifier 301 when the switch is turned on / off.

  FIG. 57 shows a known voltage application circuit using negative feedback. The load of 302 and 303 is selected by switching with switches 310 and 311. When the switch is turned on / off as in FIG. There is a general problem that spike noise occurs in the output.

FIG. 58 shows a known constant voltage generation circuit using negative feedback, in which both ends of current detection resistors 306 and 307 for measuring the current value by the current measuring unit 309 are selected to be short-circuited / non-short-circuited by the switch 310. Thus, the current detection gain is selected, but there is a general problem that spike noise occurs in the output of the operational amplifier 301 when the switch is turned on / off as in FIG.
For example, Patent Document 4 discloses a method for avoiding spike noise when changing the resistance value in the negative feedback circuit as shown in FIG. 58 in the negative feedback circuit, but requires addition of a dedicated switch and a control procedure. .

FIG. 59 shows a basic current / voltage conversion circuit in which the I / V conversion resistors 3 and 4 in the case of two ranges are paralleled and the ranges are switched by the semiconductor switches 23 and 25.
This circuit is not practical when the current to be measured is small and the influence of the leakage current of the semiconductor switch becomes an error factor. Therefore, a circuit in which measures are taken in Patent Document 1 and Patent Document 2 has been disclosed.
However, all of them have a drawback that the circuit scale becomes large.
Japanese Patent Application No. 2003-400908 Japanese Patent Application No. 2006-147509 JP 06-097775 JP2002-139520

  The problem to be solved is that, in the resistor series current / voltage conversion circuit, the diode switch is used for the disadvantage that a minute current flows due to the forward voltage due to the offset voltage of the peripheral circuit between the two terminals of the diode switch to cause a measurement error. In order to use the characteristic that the reverse leakage current becomes small when the reverse bias voltage is applied to the diode, the circuit configuration is such that the reverse bias voltage is applied to the diode switch, and the measurement error due to the leakage current is reduced. The switching circuit is to be obtained.

  In addition, the resistance parallel current is a new current / voltage conversion circuit that is different from the resistance series current / voltage conversion circuit and has a small measurement error due to the bias current of the buffer amplifier, etc., and the leakage current of the semiconductor switch, and can switch any range. / Voltage conversion circuit and multiplexed current / voltage conversion circuit.

  Furthermore, a switch circuit that reduces spike noise due to the fact that the response of the negative feedback circuit at the time of circuit switching by the switch in the resistor series current / voltage conversion circuit 1 of FIG. 40 and other general negative feedback circuits cannot be followed will be obtained. It is what.

 The range switching circuit according to claim 1 has an operational amplifier and a plurality of I / V conversion resistors connected in series or in parallel, and a diode switch and a current drive circuit are provided at one end of each I / V conversion resistor to switch the range. In a current / voltage conversion circuit that switches the range by turning the current drive circuit on and off by the circuit, the current switch is configured to apply a reverse bias voltage to the diode switch and the diode switch when the range is off. This is characterized in that the measurement error due to the leakage current of the diode switch is reduced by providing it separately for the current and the current sink.

  The range switching circuit according to claim 2 has an operational amplifier and a plurality of I / V conversion resistors connected in series or in parallel, and a diode switch and a current drive circuit are provided at one end of each I / V conversion resistor, thereby switching the range. In a current / voltage conversion circuit that switches the range by turning the current drive circuit on and off by the circuit, diode switches with a circuit that applies a reverse bias voltage when the range is off are used for the current discharge direction and the current suction direction. It is characterized in that it is provided separately and the measurement error due to the leakage current of the diode switch is reduced.

  A range switching circuit according to claim 3 is a current / voltage conversion circuit using the range switching circuit according to claim 1 or 2, wherein a diode switch of the range is applied to a current input immediately before the range is turned on. The reverse bias voltage is set in the range switching circuit so as to be reverse biased, and the input of the terminal potential on the I / V conversion resistance side of the diode switch to the range switching circuit is unnecessary. .

  A range switching circuit according to claim 4 has an operational amplifier and a plurality of I / V conversion resistors connected in series, and each of the I / V conversion resistors other than the minimum range is provided with a diode switch and a current drive circuit. In a current / voltage conversion circuit called a resistance series current / voltage conversion circuit 2 that performs an auto-range operation by a range switching circuit using a limit circuit, a voltage input section is provided to the dead zone circuit and the limit circuit from the outside, and the voltage applied to them Thus, the range on / off operation can be forcibly enabled / disabled by changing the dead band setting voltage and the limit setting voltage.

A current / voltage conversion circuit called a resistance parallel current / voltage conversion circuit according to claim 5 is:
Connects one end of a current on / off switch using a semiconductor switch and one end of an I / V conversion resistor, and provides a T-shaped circuit with a ground connection switch using an FET switch or an analog switch for the required number of ranges. Are connected to the inverting input terminal of the operational amplifier, and the I / V of each T-shaped circuit is connected to the inverting input terminal of the operational amplifier. Connect the terminal on the opposite side of the conversion resistor's ground connection switch to the output terminal of the operational amplifier. For the range to be turned on, turn on the current on / off switch and turn off the ground connection switch. Measured due to the leakage current of the semiconductor switch by turning off the current on / off switch and turning on the ground connection switch And it is characterized in that was to reduce the difference.

  The switch circuit according to claim 6 gradually decreases the gate control voltage or current at an arbitrary time constant with respect to on / off of the FET switch on / off control signal by an integrating circuit composed of a resistor, a capacitor and, if necessary, a diode. The resistance value between the drain and the source of the FET switch is gradually decreased / increased.

  The level conversion circuit according to claim 7 comprises an integrating circuit by combining a resistor, a capacitor and, if necessary, a diode with an operational amplifier, applying a predetermined reference voltage to the non-inverting input terminal of the operational amplifier, It is characterized in that the time constant of the output voltage and the voltage at the time of settling can be arbitrarily set for the on / off input signal.

  The switch circuit according to claim 8 uses the level conversion circuit of claim 7 to gradually decrease / increase the gate control voltage or current with an arbitrary time constant with respect to the on / off of the arbitrary voltage on / off control signal, In addition, by setting the voltage or current during settling to an arbitrary value, the resistance value between the drain and source of the FET switch gradually decreases / increases, and the dead time of the on / off operation can be reduced. It is.

  The negative feedback circuit according to claim 9 is a plurality of input resistors and their selection switches, or a plurality of negative feedback resistors and their selection switches, or a plurality of load circuits and their selection switches, In a negative feedback circuit using an operational amplifier circuit having items, the switch circuit according to claim 6 or 8 is used as a selection switch, and a change in the resistance value of the switch at the time of ON / OFF can follow the response of the negative feedback circuit. Thus, the time constant of the switch circuit is set so that the spike noise of the operational amplifier generated when the switch circuit is turned on / off is reduced.

  The current / voltage conversion circuit according to claim 10 uses the switch circuit according to claim 6 or 8 as a switch of the resistance parallel current / voltage conversion circuit according to claim 5, and the resistance value change of the switch at the time of on / off is changed. The time constant of the switch circuit is set so that the response of the negative feedback circuit can follow, and the operational amplifier spike noise that occurs when the switch circuit for range switching is turned on / off is reduced. Is.

  The current / voltage conversion circuit according to claim 11 is provided with an operational amplifier for error amplification and an operational amplifier for I / V conversion using an I / V conversion resistor as a negative feedback resistor, and one of the current on / off semiconductor switches. Connect the terminal to the inverting input terminal of the operational amplifier for error amplification, connect the other terminal to the inverting input terminal of the operational amplifier for I / V conversion, and connect the non-inverting input terminal of the operational amplifier for I / V conversion. The output of the operational amplifier for error amplification or the ground can be selected by the semiconductor switch for range on / off, and the semiconductor switch for current on / off and / or the semiconductor switch for range on / off are turned on / off. By doing so, it is possible to control the on / off of the current flowing through the I / V conversion resistor with less leakage current of the semiconductor switch, and the output voltage of the operational amplifier for I / V conversion and its non-inverting input The potential difference between the terminal voltage and is characterized in that comprising a voltage proportional to the current flowing through the I / V conversion resistor.

  12. The current / voltage conversion circuit according to claim 12, wherein a diode switch is used as a semiconductor switch for turning on / off the current, the diode switch, the I / V conversion resistor, and the I / V conversion. Operational amplifiers are provided for current discharge and current suction respectively, and the reverse bias voltage value to be applied when the diode switch is off is applied to the non-inverting input terminal of the operational amplifier for I / V conversion to suppress the leakage current of the diode switch. It is characterized by things.

  A current / voltage conversion circuit referred to as a multiplexed current / voltage conversion circuit according to claim 13 is the number of required ranges for a circuit related to I / V conversion for each range of the current / voltage conversion circuit according to claim 11 or claim 12. This is characterized in that it is provided in parallel, and this is combined with an error amplification operational amplifier to enable on / off control of an arbitrary range with less leakage current of the semiconductor switch.

  A current / voltage conversion circuit according to a fourteenth aspect is the multiplexed current / voltage conversion circuit according to the thirteenth aspect, wherein a resistor is provided between the semiconductor switch for current on / off and the inverting input terminal of the operational amplifier for I / V conversion. In addition, a dead band circuit is provided between the semiconductor switch for range ON / OFF and the output terminal of the error amplification operational amplifier as necessary to widen the output voltage range of the error amplification operational amplifier. .

  A current / voltage conversion circuit according to claim 15 is the multiplexed current / voltage conversion circuit according to claim 11, claim 12, claim 13, or claim 14, and a semiconductor switch for current on / off and a range on / off The switch circuit according to claim 6 or 8 is a switch circuit according to claim 6 or claim 8 of the semiconductor switch, and the switch circuit changes so that the change in the resistance value of the switch at the time of on / off can follow the response of the negative feedback circuit. It is characterized by setting a time constant and reducing spike noise of each operational amplifier due to range switching.

  A current / voltage conversion circuit according to claim 16 is the multiplexed current / voltage conversion circuit according to claim 13, 14, or 15, wherein an optimum value phase compensation capacitor is provided for each range. And a non-inverting input terminal of the operational amplifier for I / V conversion and a terminal connected to the inverting input terminal of the error amplification operational amplifier of the semiconductor switch for current on / off. is there.

  The current / voltage conversion circuit according to claim 17 has an operational amplifier and a plurality of I / V conversion resistors connected in series, and a diode switch and a current drive circuit are provided at one end of each I / V conversion resistor other than the minimum range. In a current / voltage conversion circuit called a resistance series current / voltage conversion circuit 1 that switches a range by turning the current drive circuit on / off by the range switching circuit, the input of the current drive circuit is input to the range for the range switching. 9. A switch circuit according to claim 6 or 8, wherein a selection is made between the detection voltage of the I / V conversion resistor or the output voltage of an operational amplifier for error amplification or a dead band circuit provided as necessary at the output section thereof. Set the time constant of the switch circuit so that the change of the resistance value of the switch at the time of ON / OFF becomes the speed that the response of the negative feedback circuit can follow. Is characterized in that the reducing spike noise of the operational amplifier.

The current / voltage conversion circuit according to claim 18 is a multiplexed current / voltage conversion circuit according to claim 13 or claim 14 or claim 15 and an arbitrary range of resistance series current / voltage conversion circuit or an arbitrary range number. Combined resistance series current / voltage conversion circuit according to claim 1 or claim 2 or claim 3 or claim 4 or claim 17, or multiplexed current according to claim 13 or claim 14 or claim 15 in any number of ranges Circuit elements used in combination of leakage current of semiconductor switches, buffer amplifiers, operational amplifiers, and other arithmetic circuits by combining a voltage / voltage conversion circuit and a resistance parallel current / voltage conversion circuit according to claim 5 or claim 10 of any number of ranges This is characterized in that the measurement error due to the bias current and the offset voltage is reduced.

  The range switching circuit of the present invention reduces the influence of the offset voltage of the circuit by adding a small number of components to the resistor series current / voltage conversion circuit disclosed in Patent Document 1 and Patent Document 2, and enables range on / off control arbitrarily. The effect of being able to do is obtained.

  In addition, the range switching circuit of the present invention reduces measurement errors due to leakage current of semiconductor switches and bias currents of buffer amplifiers even for minute currents such as nanoampere level and picoampere level, which were difficult to achieve in the past. The effect which can implement | achieve the current / voltage conversion circuit which was made can be acquired.

  Furthermore, by using the switch circuit using the voltage controlled variable resistor of the present invention for the negative feedback circuit, it is possible to reduce the spike noise generated in the negative feedback circuit due to the switch switching.

First, definitions of terms used in this document are shown.
In this document, the unit of voltage is [V], the unit of current is [A], the unit of resistance is [Ω], the unit of capacitor is [F], and the unit of time is [second]. If the unit is clear in context, the description may be omitted.
In addition, since the voltage and current of each part of the circuit differ only in the sign depending on the direction of the input current I and operate on the circuit in the same way as the positive and negative, the voltage and current values in the following description are positive or The absolute value will be used for explanation.

  In addition, there are cases where the symbol and the resistance value Rn are written side by side in the explanatory diagram regarding the resistance. In order to make it easy to understand, there is a case where the resistance is specified by the resistance value Rn instead of the sign when specifying the resistance within a range not causing misunderstanding.

In general, the magnitude of current is measured and measured by flowing the current through an I / V conversion resistor and measuring the voltage at both ends. This is called current / voltage conversion, and a circuit for this is called a current / voltage conversion circuit.
When the current range is wide, an I / V conversion resistor having a different value is provided for each range, and the I / V conversion resistor or the voltage signal after the I / V conversion is selected by the selection circuit. This is called range switching.
In this document, the part of the current / voltage conversion circuit that performs the range switching is called a “range switching circuit”.

  In addition, as described above, the operational amplifier disclosed in Patent Document 1 and a plurality of I / V conversion resistors connected in series have a diode switch and a current drive circuit for each I / V conversion resistor other than the minimum range. A current / voltage conversion circuit that switches the range by providing a current bypass circuit according to, and switching the current bypass circuit on and off by the range switching circuit is referred to as a “resistance series current / voltage conversion circuit 1”.

  In addition, as described above, the operational amplifier disclosed in Patent Document 2 has a plurality of I / V conversion resistors connected in series, and a diode switch and a current drive circuit are connected to each I / V conversion resistor other than the minimum range. A current bypass circuit is provided, and the current drive circuit is driven by the sum of the terminal voltage of the diode switch on the I / V conversion resistance side via the limit circuit and the voltage output of the operational amplifier via the dead band circuit, thereby automatically ranging The current / voltage conversion circuit that performs switching is referred to as “resistor series current / voltage conversion circuit 2”.

  Furthermore, the above-mentioned “resistance series current / voltage conversion circuit 1” and “resistance series current / voltage conversion circuit 2” are collectively referred to as “resistance series current / voltage conversion circuit”.

  In addition, the T-shaped circuit comprising the current on / off semiconductor switch, the I / V conversion resistor, the ground connection FET switch or the analog switch described in claim 5 can be switched by combining the required number of ranges and an operational amplifier. The current / voltage conversion circuit made possible is called a “resistance parallel current / voltage conversion circuit”.

  Further, the circuit comprising the combination of the operational amplifier for I / V conversion using the I / V conversion resistor as the negative feedback resistor, the semiconductor switch for range on / off, and the semiconductor switch for current on / off according to claim 13 as the required number of ranges. A current / voltage conversion circuit that is provided in parallel and is combined with an operational amplifier to enable range switching is referred to as a “multiplexed current / voltage conversion circuit”.

Further, as described above, in the present invention, the diode current switch characteristics shown in the characteristic examples of FIGS. 60 and 61 are used.
There are diode-connected transistors, diode-connected FETs, varistors, Zener diodes, etc. as elements having such a voltage-current characteristic equivalent to diodes. It is indicated by “switch” and is indicated by a diode symbol in the drawing.

In addition to these diode switches, this document describes a field effect transistor as a three-terminal switch having two terminals of the main circuit, so-called “source” and “drain”, and a terminal for controlling on / off, so-called “gate”. (Hereinafter referred to as FET).
The FET includes a junction type FET (hereinafter referred to as J-FET) and an insulated gate FET (hereinafter referred to as MOS-FET). Further, the J-FET includes an N channel junction type FET (hereinafter referred to as NJ-FET), P There are channel junction type FETs (hereinafter referred to as PJ-FETs), and MOS-FETs include N-channel insulated gate FETs (hereinafter referred to as NMOS-FETs), P-channel insulated gate FETs (hereinafter referred to as PMOS-FETs), etc. There is also a photo mos relay with similar functions.

  A MOS-FET generally has a built-in diode between its drain and source. In this case, if two diodes are connected in series in the reverse direction as shown in FIG. 62, they are necessary for use in the present invention. This function is equivalent to other FETs.

  The photoMOS relay has four terminals, but in actual use, as shown in FIG. 63, either the anode or the cathode of the on / off control light emitting diode is connected to the power supply or ground via a resistor. Since it is connected and used to control the flow of current from the other terminal, it is essentially three terminals, and the functions necessary for use in the invention of this document are equivalent to other FETs.

In view of the above, in this document, these are collectively referred to as “FET switches”.
In addition, there is a general analog switch as an on / off switch for an analog circuit, and it can be used as a switch in the present invention in many cases.
Accordingly, it is sufficient that the circuit has only a switching function. When any of a diode switch, FET switch, and general analog switch can be used, it is generically called “semiconductor switch”.

Further, J-FETs, MOS-FETs, photo MOS relays and the like are generally known as voltage controlled variable resistance elements, and any of them can be used in the present invention, and these are collectively referred to as FET switches.
Furthermore, when the switch circuit according to claim 6 or 8 using a voltage-controlled variable resistance (Voltage-Controlled Resistor) characteristic in which a resistance value changes in accordance with a control signal voltage of the FET switch, a “VCR switch” is used. Shall be called.

Also, in this document, when parts and circuit blocks are the same in the drawings, they are indicated by the same reference numerals or the same reference numerals with suffixes such as A, B, etc. The description will not be repeated.
Also, for convenience of exponential notation, the base e of the natural logarithm is raised to the Xth power by exp [X].
Further, the embodiments described below are merely “examples”, and various variations derived from combinations, applications, derivations, and analogies can be easily considered as methods for realizing equivalent functions. They are all within the scope of the present invention as long as they are based on the principle.
Based on the above, the best mode for carrying out the invention will be described below as an example.

FIG. 1 shows an embodiment of a resistance series current / voltage conversion circuit using the range switching circuit according to claim 1 of the present invention.
In addition, each circuit described in this document is compatible with both current input and output current input, but in actual application, it may be necessary to support only one of the input currents. The circuit related to the unnecessary current direction can be removed to reduce the circuit.

Parts equivalent to those in FIG. 42 are denoted by the same reference numerals as in FIG. The basic operation is the same as the operation of FIG. 42 described in the background art.
The output section of the range switching circuit 50 is shown in FIG. 43 and will be described below with reference to FIGS.
The current drive circuits 52 and 53 are provided with current boosters 54 and 55 as necessary when the drive current is large.

In this example, the current drive circuits 52 and 53 are constituted by an inverting addition circuit, and a negative bias −E1 is added to the output of the current drive circuit 52 by the voltage + E1 of the constant voltage source 56, and the current is generated by the voltage −E2 of the constant voltage source 57. A positive bias + E2 is added to the output of the drive circuit 53, and various variations can be easily configured by an adder / subtractor circuit using a known operational amplifier as shown in the example of FIG.
Note that the input / output relational expressions are described assuming that the resistance values in the figure are all the same.
Further, the notation in the range switching circuit 50 in FIG. 1 shows the configuration image, and the polarity of the bias power supply is opposite to that in FIG. The same applies to the following other embodiments.

The current drive circuit 52 discharges bypass current, the current drive circuit 53 sucks bypass current, and the diode switches 6 and 6A are on / off switches.
The outputs of the current drive circuits 52 and 53 appear themselves and the offset voltage and gain error of the operational amplifier 1, the range control unit 51, the buffer amplifier 10 and the like as error amplifiers connected thereto. Collectively called the offset voltage.

  Here, when the voltage + E1 having a magnitude that can cancel the positive maximum offset voltage expected in the output of the current drive circuit 52 is inverted and added, when the range 2 is off, the range control unit 51 sets V21 = V2. Even if the circuit 52 has a positive offset voltage, it is canceled by -E1 and the both ends of the diode switch 6 are reverse-biased, so that the leakage current becomes almost 0A.

  Similarly, if the voltage -E2 having a magnitude that can cancel the negative maximum offset voltage expected in the output of the current drive circuit 53 is inverted and added, the range control unit 51 sets V21 = V2 when the range 2 is off. Even if the drive circuit 53 has a negative offset voltage, it is canceled by + E2 and both ends of the diode switch 6A are reverse-biased, so that the leakage current becomes almost 0A.

From the above, it can be seen that according to the circuit configuration of FIG. 1, the diode switches 6 and 6A are reverse-biased when the range 2 is off, and a current / voltage conversion circuit with a small measurement error due to leakage current can be obtained.
The above operation is the same even if the number of ranges increases.
If the reverse bias voltage of the diode switch is unnecessarily large, a reverse leakage current of the diode switch, which becomes an error factor, is generated, and the change width of V1 and V21 when the range 2 is turned on / off increases, resulting in a slow circuit response. Therefore, the reverse bias voltage should be set not to be unnecessarily large.

FIG. 2 shows another embodiment of the resistance series current / voltage conversion circuit using the range switching circuit according to claim 1 of the present invention.
The output section of the range switching circuit 60 is shown in FIG. 44 and will be described below with reference to FIGS.
The difference from the first embodiment is that the output unit of the range control unit 61 is divided into a + output unit 68 and a -output unit 69, and the operation is the same as that of the first embodiment.
As shown in the graph of FIG. 2, the + output unit 68 keeps V21 at 0V or higher, and the -output unit 69 keeps V22 at 0V or lower.
This is advantageous in that the range switching operation when the direction of the input current I is reversed becomes faster.
The above is the same even if the number of ranges increases.

FIG. 3 shows the same range switching circuit as the resistance series current / voltage conversion circuit using the range switching circuit according to claim 1 of the present invention, and the current / voltage for driving the I / V conversion resistors 3, 4 and 5 arranged in parallel. This is an embodiment in the case of three ranges indicating that the present invention can also be applied to a conversion circuit.
The buffer amplifiers 10 and 11 are provided as necessary.
In the present embodiment, the right terminals of the I / V conversion resistors 3, 4, 5 are directly connected to the inverting input terminal of the operational amplifier 1, so that their potentials become 0V.
Accordingly, the input current I is the sum of the currents flowing through the I / V conversion resistors 3, 4 and 5. The arithmetic circuit 2 measures the potentials V1, V2 and V3 of the left terminals of R1, R2 and R3,
I = V1 / R1 + V2 / R2 + V3 / R3 (5)
The value of the input current I can be obtained by the following calculation.

  In this circuit, V2 may be 0 V when range 2 is off, and V3 may be 0 V when range 3 is off. Therefore, unlike the resistance series current / voltage conversion circuit, the range switching circuits 50 and 50A are Since it is sufficient to output 0 V when the range is off, there is no need to put the potentials V2 and V3 on the right side of the diode switch into the operating conditions, and it is advantageous to reduce the circuit accordingly.

Although the I / V conversion resistor 3 is always on, it may be removed and all the I / V conversion resistors may be controlled to be turned on / off.
The above is the same even if the number of ranges increases.

FIG. 4 shows an embodiment of a resistance series current / voltage conversion circuit using the range switching circuit of claim 2 of the present invention.
The reverse bias application circuit 70 is for applying a reverse bias voltage to the diode switches 6 and 6A when the range 2 is off.
71 is a negative constant voltage source of −E1X, 72 is a positive constant voltage source of + E2X, 73 and 74 are diodes, 75 is a resistor having a resistance value R2A, 76 is a resistor having a resistance value R2B, and others are shown in FIG. Same as 1.

The output of the range switching circuit 50 appears by adding itself and offset voltages of the operational amplifier 1 and the buffer amplifier 10 connected thereto.
-E1X, R2A so that the voltage obtained by dividing the potential between V21 and -E1X to which the positive maximum offset voltage value expected in the range switching circuit 50 is added by the diodes 73 and R2A becomes smaller than V2 when the range 2 is off. Is set to reverse bias the diode switch 6.
Similarly, + E2X and R2B are set so that the diode switch 6A is reverse-biased when the range 2 is off.

Here, when range 2 is off, V21 = V2 is set by the range switching circuit 50, so that both ends of the diode switches 6 and 6A are reverse-biased, and the leakage current becomes approximately 0A.
From the above, it can be seen that the circuit configuration of FIG. 4 can provide a current / voltage conversion circuit with a small measurement error due to the leakage current of the diode.

The reverse bias applying circuit 70 may be a known bias generating circuit as long as the reverse bias can be applied to the diode switches 6 and 6A when the range 2 is off. For example, the diodes 73 and 74 have resistances with appropriate values if the bypass current is small. But it ’s okay. Alternatively, the resistors 75 and 76 can be replaced with a constant current circuit such as a constant current diode or FET.
Here, since the current flowing through the voltage dividing circuit in the reverse bias applying circuit 70 does not flow through the I / V conversion resistors R1 and R2, it is clear that the measurement accuracy is not affected.
Further, although there is one range control unit in the range switching circuit 50, it may be divided for discharge and suction as shown in FIG.

  If the reverse bias voltage of the diode switches 6 and 6A is unnecessarily large, the reverse leakage current of the diode, which becomes an error factor, increases, and the change width of V1 and V21 when the range 2 is turned on / off increases, and the circuit Since the response may be delayed, the reverse bias voltage should be set not to be unnecessarily large.

  When the range switching circuit of claim 2 is connected in parallel with the I / V conversion resistor, the range switching circuit 50 of FIG. 3 may be replaced with the reverse bias application circuit 70 of FIG.

FIG. 5 shows an embodiment of a resistance series current / voltage conversion circuit using the range switching circuit of claim 3 of the present invention.
The reverse bias voltage of the range switching circuit 50 is set to the magnitudes −EL21 and + EL22 at which the diode switches 6 and 6A are reverse biased with respect to the input current when the range 2 is turned on.
As a result, even if the voltage V2 at the right end of the diode switch 6, 6A is not included in the operating condition of the range switching circuit 50, the diode switch 6, 6A is reverse-biased even when V21 is 0V while the range 2 is off, and the leakage current is 0A. become.
As a result, there is an advantage that a circuit for inputting the potential V2 to the range switching circuit 50 becomes unnecessary.
The above is the same even if the number of ranges increases.

FIG. 6 shows an embodiment in which the resistance series current / voltage conversion circuit 2 using the range switching circuit according to claim 4 of the present invention has 3 ranges.
The range switching circuits 110 and 110A are provided with an external voltage input section corresponding to the dead band circuit and limit circuit of the resistance series current / voltage conversion circuit 2, and the dead band setting voltage and limit setting voltage are changed by the voltage applied thereto. By doing so, the range on / off operation can be forcibly enabled / disabled.

FIG. 45 shows an example of the range switching circuits 110 and 110A. The dead zone circuit 111 is known, and the dead zone setting voltages + Edb and -Edb are set by the constant voltage sources 114 and 115.
The limit circuit 112 is also known, and the limit setting voltages + Elmt and −Elmt are set by the constant voltage sources 116 and 117.
In this example, the resistance values of the resistors in the circuit are all equal, and accordingly, the gains of all the inverting amplifiers are -1.

The inverting amplifier 113 inverts the range on / off disable control input Vcont.
As a result, the range on / off disable control input Vcont is added to the deadband setting voltage of the deadband circuit 111 and the limit setting voltage of the limit circuit 112, and these setting voltages can be changed by Vcont.
The current drive circuit 118 also includes an inversion addition function of the output of the dead zone circuit 111 and the output of the limit circuit 112.
Here, if Vcont is set to 0 V, the current switching circuit 118 and the dead zone circuit 111 are not affected, and the range switching circuit is enabled.

If the voltage Vdis is larger than the expected Vcont (Vdbin−Edb) and larger than the expected (Vlmtin−Elmt), the output of the dead band circuit 111 becomes 0 V, and the limiter function of the limit circuit 112 is disabled. Therefore, Vlmtin is output as it is to the output of the current drive circuit 118, and the range switching circuit is disabled.
Note that Vdis may be a constant value (fixed value), and it is an advantage that compatibility with a comparator circuit, an inverter circuit, or the like is good.

  In FIG. 6, if the voltages necessary for disabling the on / off disable control signals for range 2 and range 3 are Vdis2 and Vdis3, respectively, the arithmetic circuit 2 generates the range 2 on / off disable control signal. If the 0V or Vdis2, range 3 on / off disable control signal is switched to 0V or Vdis3, the range switching circuits 110 and 110A can be arbitrarily enabled / disabled, and the disclosed resistance series current / voltage conversion circuit 2 Will be much easier to use.

  It is also advantageous that the range switching circuit of claim 1 can be easily realized by adding a reverse bias voltage application circuit as shown in FIG. 43 or 44 to the current drive circuit 118.

FIG. 7 is a basic circuit example of a resistance parallel current / voltage conversion circuit according to claim 5 of the present invention.
For the sake of clarity of explanation, a current / voltage conversion circuit with two ranges having I / V conversion resistors 3 and 4 is used.
The operational amplifier 1 is used as an error amplifier, and the current booster 32 is included when the current driving capability of the operational amplifier 1 is insufficient, and is not essential.

The current on / off switches 23 and 25 are semiconductor switches, and the ground connection switches 24 and 26 are FET switches or analog switches.
Range 1 is turned on / off by the range 1 on / off control signal.
When range 1 is on, switch 23 is turned on and switch 24 is turned off. When range 1 is off, switch 23 is turned off and switch 24 is turned on. In other words, the ON / OFF of the switch 23 and the switch 24 is opposite to each other, and the inverter 27 shows an image of the relationship, and is not essential. When both ranges are ON and an overlap period is required The range 1 on / off control signal may be prepared for each switch individually, and the arithmetic circuit 2 may perform control so that both ranges overlap.

  The range 2 is turned on / off by the range 2 on / off control signal, and the control method of the switches 25 and 26 is the same as that of the range 1.

Since this circuit uses the fact that the on-resistance value of the switch is sufficiently small with respect to the I / V conversion resistance value and the off-resistance value of the switch is sufficiently large, a specific numerical example is provided for clarity of explanation. This is explained below.
Range 1 is 100 μA full scale and range 2 is 1 mA full scale.
The resistance value R1 of the I / V conversion resistor 3 is 100 kΩ, the resistance value R2 of the I / V conversion resistor 4 is 10 kΩ, the on-resistance of the switches 23, 24, 25, and 26 is 10Ω, and when off, it is a circuit Is infinitely large enough to be treated as completely off. The resistance values of these switches can be realized by general FETs or analog switches and are realistic values.

The operation will be described with reference to FIG. This figure shows the case where range 1 is on and range 2 is off, with switches 23 and 26 turned on and switches 24 and 25 turned off.
In this case, the input current I to be measured is driven by the operational amplifier 1 so as to flow through the route indicated by I1 through the I / V conversion resistor 3, so that I = I1. If the output voltage is V0,
I = V0 / (R1 + r) (6)
become.
Here, if an error of about 0.01% is allowed, 100 kΩ of R1 is sufficiently larger than the on-resistance 10 Ω of the switch 23 and can be regarded as R1 >> r.
I≈V0 / R1 (7)
Thus, the value of the input current I can be obtained from the voltage V0 and the resistance value R1 by the arithmetic circuit 2.

Here, if the input current I is 100 μA which is the full scale value of the range 1, V0 becomes 10V, so the voltage V22 across the switch 26 in the range 2 is divided by R2 and r to become about 10 mV.
Since the left terminal of the switch 25 which is off at this time is 0 V which is the same as the inverting input terminal voltage of the operational amplifier 1, the voltage V21 across the switch 25 is about 10 mV, equal to V22.

Generally, even when an FET switch is turned off, a leakage current Ids flows according to the voltage across the terminal (drain-source voltage Vds). As an example, FIG. 65 shows an example of Vds-Ids characteristics when the NJ-FET is off. As can be seen from this, when Vds is large, the leakage current increases. However, when Vds is close to 0 V, the leakage current is close to 0 A and decreases to a negligible level.
In the case of the above example, by using an FET switch in which V21 is as small as 10 mV and the leakage current at the time of off is sufficiently small with respect to the full scale 100 μA of range 1, FIG. It can be seen that this is a current / voltage conversion circuit.
In the above example, if the off-time Vds is 10 mV and the leakage current is 0.1 μA or less, the error due to this is 0.1% or less, and such an FET is readily available.

If there is no ground connection by the switch 26 in FIG. 8, V21 becomes 10V, and the leakage current of the switch 25 becomes large, and the possibility that the error is not negligible increases. Therefore, the effectiveness of the switch 26 can be understood.
In the case of the above example, the I / V conversion resistor 4 becomes a load of the operational amplifier 1 and a current I2 passing through the switch 26 flows. However, it is independent of the input current I and does not affect the measurement accuracy.

When range 1 is off and range 2 is on, switches 24 and 25 are turned on and switches 23 and 26 are turned off. (Not shown)
Then, the input current I to be measured is driven by the operational amplifier 1 so as to flow through the I / V conversion resistor 4 and the switch 25. At this time, if the output voltage of the operational amplifier is V0, I = V0 / (R2 + r).・ (8)
become.
Here, if an error of about 0.1% is allowed, 10 kΩ of R2 is sufficiently larger than the on-resistance 10 Ω of the switch 25 and can be regarded as R2 >> r.
I≈V0 / R2 (9)
Thus, the value of the input current I can be obtained from the voltage V0 and the resistance value R2 by the arithmetic circuit 2.

Here, if the input current I is 1 mA of the full scale value of the range 2, V0 becomes 10V, so the voltage V12 across the switch 24 in the range 1 is divided by R1 and r to become about 1 mV.
Since the left terminal of the switch 23 which is off at this time is 0 V which is the same as the inverting input terminal voltage of the operational amplifier 1, the voltage V11 across the switch 23 is about 1 mV, equal to V12, and the leakage current is reduced to a negligible level.

Also in this case, if there is no ground connection by the switch 24, V11 becomes 10V, the leakage current of the switch 23 becomes large, and there is a high possibility that the error cannot be ignored.
In the above case, the I / V conversion resistor 3 serves as a load of the operational amplifier 1 and a current flows through the switch 24, but is independent of the input current I and does not affect the measurement accuracy.

  However, since the voltage between both terminals of the switches 23 and 25 at the time of OFF is not completely 0V, it is not suitable for measuring a minute current whose leakage current cannot be ignored.

From the above, it can be seen that the range of the circuit of FIG. 7 can be switched with little influence on the measurement accuracy of the leakage current of the switch, and the number of ranges can be easily increased to 3 or more by the same method.
Further, this resistance parallel current / voltage conversion circuit may simultaneously turn on a plurality of ranges and set the parallel value of these I / V conversion resistors as the I / V conversion resistance value.
In the method of this embodiment, a current booster 32 is provided when the operational capability of the operational amplifier 1 is insufficient because current flows through all I / V conversion resistors regardless of on / off.

FIG. 9 shows another embodiment of the resistance parallel current / voltage conversion circuit according to claim 5 of the present invention, which is an extension of FIG.
The semiconductor switches 23 and 25 are FET switches, analog switches, or diode switches, and the on-resistances of the FET switches and analog switches may not be negligible with respect to the I / V conversion resistance.

The voltage signals V11 and V21 are taken out from the semiconductor switches 24 and 26 side of the I / V conversion resistors 3 and 4 and connected to the arithmetic circuit 2, and the difference between the voltage signal and the output voltage V0 of the operational amplifier 1 or the current booster 32 is expressed as I. The both-end signals V1 and V2 of the / V conversion resistor are used, and the current is calculated in the same manner as in the seventh embodiment.
The differential amplifiers 20 and 20A indicate functions, and a differential amplifier may be used in practice. Alternatively, V0, V11, and V21 may be A / D converted and then calculated by software to obtain a potential difference.
In FIG. 9, the on-resistance of the semiconductor switches 23 and 25 is relatively large with respect to the I / V conversion resistor, and the voltage across the semiconductor switch when the range is on cannot be ignored with respect to the voltage across the I / V conversion resistor. This is particularly effective in the case of a diode switch in which the voltage between both ends is about 0.6V.

FIG. 10 shows an embodiment of a switch circuit called a VCR switch using the FET switch according to claim 6 of the present invention.
In the present invention, the FET switch is not simply turned on / off, but the on / off control signal is changed from a maximum value to a minimum value (from a minimum value) to a minimum value when the switch resistance is turned on. From OFF to OFF, the switch resistance value is gradually changed (gradually increased) from the minimum value to the maximum value.

  FIG. 64 shows an example of the characteristics of the gate-source voltage Vgs and the drain-source resistance Rds of the NJ-FET. From this figure, it can be seen that when Vgs is changed, Rds changes greatly, and there is a characteristic of a voltage controlled variable resistor.

FIG. 10 is a circuit example of the VCR switch 400 when an NJ-FET is used as the voltage control variable resistance element.
The terminals indicated by S and D of the VCR switch 400 perform a switching operation, and the terminal indicated by C is a terminal that receives a switch ON / OFF control signal.

Reference numeral 401 denotes an NJ-FET, and for the following description, the resistance value r is assumed to be infinitely large enough to be handled as being completely off at the maximum, and 10Ω at the minimum.
Reference numeral 402 denotes a gate-source bias resistor of about several MΩ, and reference numeral 403 denotes a gate reverse bias prevention diode.
Reference numeral 420 denotes a level conversion circuit for converting the gate on / off signal into a voltage level necessary for gate control of the FET, and a level conversion unit 430 for converting the gate on / off control signal level into the gate control signal level VcL / VcH; It consists of a CR integration circuit 440. VcL / VcH are two kinds of power supply voltages sufficient to turn on / off the FET.
Reference numeral 431 denotes an NPN transistor, reference numeral 432 denotes a PNP transistor, and reference numeral 433 denotes a resistor having a resistance value R0.

Reference numerals 441 and 442 denote resistors, reference numerals 443 and 444 denote diodes, and reference numeral 445 denotes a capacitor. The rise time constant (R0 + R1) · C and the fall time constant R2 · C can be individually set by the diode.
In the case of R1> R2, the connection of FIG. 11 is made using R2X where R2 = R1 // R2X, and in the case of R1 <R2, the connection is made as shown in FIG. 12 using R1X where R1 = R1X // R2. Alternatively, either one of 444 and 444 may be unnecessary. If R1 = R2, the resistor 442 and the diodes 443 and 444 may be omitted, and only the resistor 441 may be used.

When the CR integration circuit 440 is not provided, FIG. 10 shows a known FET gate control circuit, and a detailed description of its operation is omitted.
In this case, the gate control circuit output voltage V2 becomes one of the values of VcL / VcH according to the gate on / off control signal H / L, and the transition between them becomes a steep rising and falling waveform, and the drain of the FET The resistance value between the sources also changes abruptly between the maximum value and the minimum value.

When the CR integration circuit 440 is inserted, the gate control circuit output voltage V2 changes exponentially according to the gate on / off control signal H / L. For the sake of rough estimation, the forward voltage of the diodes 443 and 444 can be ignored, the elapsed time from the change of the gate on / off signal is t [seconds], and the time constant at the rise is τ1, and the gate control circuit output For voltage V2,
τ1 = (RO + R1) · C (10)
V2 = (VcH-VcL) ・ (1-exp [-t / τ1]) + VcL (11)
If the time constant at the fall is τ2, τ2 = R2 ・ C (12)
V2 = (VcH-VcL) · exp [-t / τ2] + VcL (13)
Holds.
A schematic waveform is shown as “waveform by CR integration circuit” in FIG.

In accordance with the change in the output voltage of the gate control circuit, the resistance value between the drain and source of the FET gradually decreases / increases between the maximum value and the minimum value.
Therefore, when the VCR switch 400 applies the gate on / off control signal to the C terminal, the resistance value between the S and D terminals gradually decreases / increases between the maximum value and the minimum value. Switch. The degree of looseness is determined by the time constant due to CR and the characteristics of FET Vgs-Rds.

However, in this VCR switch, the change in the resistance value between the gate control circuit output voltage and the S-D terminal is usually monotonously increased or monotonously decreased, but not necessarily in a linear relationship.
It should be noted that the application method of the gate voltage or the light emitting diode current in the case of the photo moss relay is different in the FET other than the NJ-FET, but a circuit that can easily perform the same operation can be obtained by applying this embodiment. .
Further, when the leakage current from the source to the gate of the NJ-FET of FIG. 10 cannot be ignored, it can be improved by using a MOS-FET or a photo moss relay.

Reference numeral 420 in FIG. 13 is an embodiment of the level conversion circuit according to claim 7 of the present invention, and shows a case where an NJ-FET is driven as a voltage control variable resistor.
Reference numeral 421 denotes an operational amplifier that forms part of an integration circuit.
Reference numeral 422 denotes a resistor having a resistance value R1, 423 denotes a resistor having a resistance value R2, 424 denotes a resistor R3, and 427 denotes an integrating capacitor having a capacitance C, which is a component of an integrating circuit including an operational amplifier 421.

Reference numeral 425 denotes a resistor having a resistance value R4, and reference numeral 426 denotes a resistor having a resistance value R5. The power supply + V and −V of the operational amplifier 421 are divided and connected to the non-inverting input terminal of the operational amplifier 421 to generate the operation reference voltage VS. To do.
It should be noted that a necessary voltage value VS may be obtained by appropriately dividing an arbitrary power source with a resistor even if it is not a ± V power source.

Reference numerals 428 and 429 denote diodes that enable R1 when the gate on / off control signal is H, and enable R2 when the gate ON / OFF control signal is L.
In the case of R1> R2, the connection of FIG. 14 is made using R2X where R2 = R1 // R2X, and in the case of R1 <R2, the connection is made as shown in FIG. 15 using R1X where R1 = R1X // R2. Alternatively, either one of 429 and 429 can be omitted. If R1 = R2, the resistor 423 and the diodes 428 and 429 are not required and only the resistor 422 may be used.
For the sake of clarity, the following calculation formula is used for rough estimation, and the forward voltages of the diodes 428 and 429 are assumed to be 0 V and can be ignored.

When the gate on / off control signal voltage V1 is V1L when L is input and the voltage after settling at the rise of V2 is V2H, the operational amplifier 421 has an inverting input terminal potential equal to the non-inverting input terminal potential VS. Since negative feedback control is performed by 421,
(V1L-VS) / R2 = (VS-V2H) / R3 (14)
When the gate on / off control signal voltage V1 is V1H when H is input and the voltage after settling at the fall of V2 is V2L,
(V1H-VS) / R1 = (VS-V2L) / R3 (15)
Holds.

On the other hand, transiently, the gate control circuit output voltage V2 changes exponentially according to the H / L of the gate on / off control signal.
Assuming that the elapsed time from the change of the gate on / off control signal V1 is t [seconds] and the time constant at the fall of V1 is τ1, the gate control circuit output voltage V2 is
τ1 = R2 ・ R3 ・ C / (R2 + R3) (16)
V2 = (V2H-V2L) ・ (1-exp [-t / τ1]) + V2L (17)
Assuming that the time constant at the rise of V1 is τ2, τ2 = R1, R3, C / (R1 + R3) (18)
V2 = (V2H-V2L) · exp [-t / τ2] + V2L (19)
Holds.

Also, when VS divides the power supply + V and -V with R4 and R5,
VS = (+ V-(-V)) ・ R5 / (R4 + R5) + (-V) (20)
Holds.
A schematic waveform is shown as “waveform by operational amplifier circuit” in FIG.

Assuming that the gate on / off control signal voltages V1L and V1H, the target values τ1 and τ2 of the time constant, and the target values V2H and V2L of the settling voltage, R1, R2, R3 using the equations (14) to (20) , R4, R5, and C can be determined.
In other words, according to the level conversion circuit 420 of FIG. 13, without using a dedicated power supply and many components, the gate voltage is gradually reduced / increased at an arbitrary time constant with respect to an arbitrary gate on / off control signal voltage V1, and the voltage is increased to an arbitrary voltage. It can be seen that the gate control circuit output voltage V2 can be obtained.

  Note that although a gate voltage application method is different in an FET other than the NJ-FET, a circuit that easily performs the same operation can be obtained by applying this embodiment.

Reference numeral 400 in FIG. 13 is an embodiment of a switch circuit using an FET switch according to claim 8 of the present invention. Hereinafter, this is also referred to as a VCR switch, but it can be substituted for the VCR switch by the CR integration circuit of FIG.
That is, the level control circuit according to claim 7 is used to gradually decrease / increase the gate control voltage or current at an arbitrary time constant with respect to on / off of an arbitrary voltage on / off control signal, and By setting the current to an arbitrary value, the resistance value between the drain and the source of the FET switch gradually decreases / increases, and the operation is as described in the tenth embodiment.
It will be described below that the dead time for the on / off operation of the VCR switch can be reduced.

FIG. 16 is a time chart of the gate on / off control signal V1 and the gate control circuit output voltage V2. The dead time will be described with reference to FIG.
In the gate control circuit output voltage V2, when the voltage that maximizes the drain-source resistance Rds of the FET is VgsL, and the voltage that minimizes the voltage is VgsH, the Rds variable region is between them. Above the switch-off region, VgsH, Rds is the minimum region, that is, the switch-on region.

VgsL and VgsH are values determined by the electrical characteristics of the FET and the peak voltage of the input signal applied to the drain or source, and differ depending on individual circuit specifications.
In the case of the “waveform by the CR integration circuit” in FIG. 10, the period T1 from when the gate on / off control signal becomes L to V2 from VcL to VgsL remains unchanged at the maximum value of Rds. It is.
A period T2 from VgsL to VgsH is a period during which Rds gradually decreases, and the time or slope thereof can be adjusted by the time constant of the CR integration circuit.
In the period T3 from VgsH to VcH, Rds remains at the minimum value and does not change.

Similarly, a period T4 from VcH to VgsH after the gate on / off control signal becomes H is a dead time when viewed as an operation time because Rds remains the minimum value and does not change.
A period T5 from VgsH to VgsL is a period in which Rds gradually increases, and the time or slope thereof can be adjusted by the time constant of the CR integration circuit.
In the period T6 from VgsL to VcL, Rds remains the minimum value and does not change.

From the above, in order to reduce the dead time, the power supply voltage VcL should be close to VgsL and the power supply voltage VcH should be close to VgsH.
However, in general, it is difficult to prepare a power supply that generates a voltage close to VgsL and VgsH that take various values according to circuit specifications and FET characteristics, and is greatly different from VgsL and VgsH. The power source must be used, and in the case of FIG. 10, the dead time is often increased.

Next, the dead time of the VCR switch of FIG. 13 using the level conversion circuit of claim 7 will be described.
Looking at the “waveform by the operational amplifier circuit” in FIG. 16, the period T11 from when the gate on / off control signal becomes L to V2 from V2L to VgsL is the maximum value of Rds and does not change. It is a dead time.
A period T12 in which V2 is from VgsL to VgsH is a period in which Rds gradually decreases, and the time or slope thereof can be adjusted by the time constant of the integration circuit.
In the period T13 from VgsH to V2H, Rds remains the minimum value and does not change.

Similarly, during the period T14 from V2H to VgsH after the gate on / off control signal becomes H, Rds remains the minimum value and does not change.
A period T15 from VgsH to VgsL is a period in which Rds gradually increases, and the time or slope thereof can be adjusted by the time constant of the integration circuit.
In the period T16 from VgsL to V2L, Rds remains the minimum value and does not change.

  From the above, it can be seen that in order to reduce the dead times T11 and T13 at the rise of V2 and the dead times T14 and T16 at the fall of V2, it is sufficient to set V2L close to VgsL and V2H close to VgsH. As described in the tenth embodiment, the switch circuit according to the eighth aspect using the level conversion circuit according to the seventh aspect can achieve this.

  That is, since the VCR switch using the CR integration circuit of FIG. 10 has difficulty in making the power supply voltages VcH and VcL optimum values, the output voltage of the gate control circuit after settling becomes larger than necessary, and the dead time at ON / OFF is large. However, the VCR switch of FIG. 13 can arbitrarily set the output voltage of the gate control circuit after settling, so the on / off time is set to a minimum and the switch time is reduced. I can do it.

However, even in this VCR switch, the change in the resistance value between the gate control circuit output voltage and the S-D terminal is usually monotonously increased or monotonously decreased, but not necessarily in a linear relationship.
Further, when the leakage current from the source to the gate of the NJ-FET of FIG. 13 cannot be ignored, it can be improved by using a MOS-FET or a photo MOS relay.

FIG. 17 shows an embodiment in which claim 9 is applied to the negative feedback circuit of FIG.
Reference numerals 400 and 400A denote VCR switches which are replaced with the switches 310 and 311 in FIG.
In the present embodiment, the resistance values of the switches 310 and 311 and the VCR switches 400 and 400A are treated as 0Ω when turned on and infinity when turned off for clarity of explanation.

In FIG. 18, a switch 310 and a resistor 304 having a resistance value R11 are connected in series, and the switch 310 is replaced with a VCR switch 400.
In the case of using the former switch 310, the series combined resistance value R becomes infinite when the switch on / off signal (not shown) is turned off, and becomes R11 when turned on, and the series combined resistance value R becomes infinite by the switch on / off. And R11 change abruptly.
On the other hand, when the latter VCR switch 400 is used, the series resistance value R becomes infinite when the VCR switch is off, and becomes R11 when the VCR switch is on, and the series combined resistance value R gradually decreases between infinity and R11 when the switch is turned on / off. / Increase gradually.

  Accordingly, the input resistors 304 and 305 connected in series with the VCR switch of FIG. 17 gradually decrease / increase as the gate on / off control signal is turned on / off, and the resistors and capacitors (not shown) of the integration circuit of the VCR switches 400 and 400A. ) Is appropriately selected so that the change in the resistance value of the switch at the time of ON / OFF becomes a speed at which the response of the negative feedback circuit can follow, the spike noise of the operational amplifier 301 can be reduced.

Similarly, consider replacing the switch 310 of FIG. 56 with the VCR switch 400.
In FIG. 19, a switch 310 and a resistor 307 having a resistance value R32 are connected in parallel, and the switch 310 is replaced with a VCR switch 400.
In the case of using the former switch 310, the parallel combined resistance value R is R32 when the switch on / off signal (not shown) is turned off, and becomes 0Ω when the switch is turned on, and the parallel combined resistance value R becomes 0Ω with R32 when the switch is turned on / off. Change rapidly between.
On the other hand, when the latter VCR switch 400 is used, the parallel resistance value R is R32 when the VCR switch is off and 0Ω when the switch is on, and the parallel combined resistance value R gradually decreases / increases between R32 and 0Ω by switching on / off. To do.

  56. If the switch 310 connected in parallel with the resistor 307 in FIG. 56 is replaced with a VCR switch, the parallel resistance value gradually decreases / increases with the on / off of the gate on / off control signal, and the integration circuit in the VCR switch Spike noise of the operational amplifier 301 can be reduced by appropriately selecting a resistor and a capacitor (not shown) so that the change in the resistance value of the switch at the time of ON / OFF becomes a speed at which the response of the negative feedback circuit can follow. it can.

Similarly to the above, the switches 310 and 311 in FIGS. 54, 55, 57, and 58 are replaced with VCR switches (not shown), and the resistors and capacitors of the integration circuits in the VCR switches are appropriately selected to turn on / off. Spike noise of the operational amplifier 301 can be reduced if the change in the resistance value of the switch at the time of turning off is such that the response of the negative feedback circuit can follow.
When the switch is in the negative feedback loop as shown in FIGS. 54 and 55, since the loop is not opened, two switches are simultaneously turned on at the time of switching, and the period in which all switches are turned off is set. It is necessary not to have it.

FIG. 20 is a circuit example of a resistance parallel current / voltage conversion circuit according to claim 10.
This is obtained by replacing the semiconductor switches 23, 24, 25, and 26 in FIG. 7 with VCR switches 400, 400A, 400B, and 400C.
It has already been explained that the range can be switched with little influence on the measurement accuracy of the leakage current of the semiconductor switch, and the VCR switch has the same effect.

The resistance and capacitor (not shown) of the integration circuit in each VCR switch in FIG. 20 are appropriately selected so that the change in the resistance value of the switch at the time of ON / OFF becomes a speed at which the response of the negative feedback circuit can follow. For example, it is possible to obtain a resistance parallel current / voltage conversion circuit with less spike noise of the operational amplifier 1 when the range is switched.
Since it has been described in the twelfth embodiment, the description of its operation is omitted.

FIG. 21 is a basic circuit example of the number of ranges 1 of the multiplexed current / voltage conversion circuit according to claim 11 of the present invention, and the range is referred to as range 1.
The current on / off semiconductor switch 23 is on / off controlled by a range on / off control signal that is an output of the arithmetic circuit 2, and is input to an analog switch, a photo moss relay, an FET, a transistor, a diode switch, a mechanical relay, or the like. A general switching element may be used as long as the current can be turned on / off.

The resistor 14 and the switch 15 are for preventing the output from being saturated when the negative feedback loop of the operational amplifier 1 is opened when the range 1 is off. When the range 1 is off, the switch 15 is turned on to resist the input current I. 14, the operational amplifier 1 is normally negatively fed back, and if any other range is added and any range is always turned on, the resistor 14 and the switch 15 may be omitted. When the number of ranges is 1, the switch 15 is turned off when the range 1 is on.
As a result, the output voltage V0 of the operational amplifier 1 is controlled so that its inverting input terminal is always 0V regardless of the magnitude of the input current I. This is assumed in the following explanation.
Note that the operation of the resistor 14 and the switch 15 is not directly related to the original current / voltage conversion function, and thus will not be described in the following description.

The range on / off switch circuit 120 is on / off controlled by a range on / off control signal that is an output of the arithmetic circuit 2, and turns on / off analog signals such as analog switches, photo moss relays, FETs, transistors, and mechanical relays. If it can be turned off, a general switch element may be used.
The resistor 33 pulls down the non-inverting input terminal of the operational amplifier 12 to the ground when the switch circuit 120 is off.

FIG. 46 shows another circuit example of the switch circuit 120, 121 is a known dead-zone circuit, and 122 is an inverting amplifier.
In this example, the resistance values of the resistors in the circuit of FIG. 46 are all equal, and accordingly, the gains of all the inverting amplifiers are −1.
When the on / off control signal connected to Vcont is set to 0V, the input Vin is output to Vout as it is.
When the on / off control signal is set to a voltage Vdis that is larger than the maximum value expected of Vin and is input to Vcont, it acts as a deadband setting voltage of the deadband circuit 121 and Vout becomes 0V.
From the above, it can be seen that FIG. 46 performs a switch operation that is on / off controlled by the voltage of Vcont. According to this switch, the switch operation becomes gentle, and there is an effect that the spike noise of each operational amplifier output due to the fact that the response of the negative feedback circuit cannot follow is reduced.
Note that Vdis may be a constant value (fixed value), and it is an advantage that compatibility with a comparator, an inverter, or the like is good.

An I / V conversion resistor 3 in FIG. 21 is an I / V conversion resistor having a resistance value R1, and constitutes an I / V conversion circuit together with the operational amplifier 12.
The buffer amplifier 10 is for buffering the non-inverting input terminal voltage of the operational amplifier 12 for I / V conversion and passing it to the arithmetic circuit 2, and may be provided as necessary.

The circuit operation of FIG. 21 will be described below.
The operational amplifier 12 for I / V conversion controls the output voltage V11 so that the potential of the inverting input terminal becomes equal to the non-inverting input terminal potential V12 by the negative feedback operation.
Accordingly, when the range on / off switch circuit 120 and the current on / off semiconductor switch 23 are turned off, V12 is pulled down to the ground by the resistor 33 and becomes 0V, and the inverting input terminal potential is also 0V. Here, since the potential of the inverting input terminal of the operational amplifier 1 is controlled to be always 0V, as a result, the voltage between both terminals of the current on / off semiconductor switch 23 is 0V and the leakage current is extremely small. The current flowing through the I / V conversion resistor 3 is 0 A, that is, the range 1 is turned off.

When the range on / off switch circuit 120 and the current on / off semiconductor switch 23 are turned on, V12 becomes a voltage V12 obtained by subtracting the voltage drop of the switch circuit 120 from V0, and the inversion of the operational amplifier 12 for I / V conversion. The potential at the input terminal is also the same potential.
As a result, the potential difference between both ends of the current on / off semiconductor switch 23 becomes V12, and the input current I is driven via the I / V conversion resistor 3 by the operational amplifier 12 for I / V conversion. become.

At this time, the current value I flowing through the I / V conversion resistor 3 can be obtained by dividing the potential difference between both ends by R1, but the inverting input terminal potential and the non-inverting input terminal potential V12 of the operational amplifier 12 for I / V conversion are Therefore, the current value I is obtained by calculating the potential difference V1 by the arithmetic circuit 2 using the output V11 and the non-inverting input terminal potential V12 and dividing by the R1. That is,
I = (V11−V12) / R1
= V1 / R1 (21)
become.

The feature of this circuit is that current ON / OFF control is possible, and the potential difference V1 between the output voltage of the operational amplifier 12 for I / V conversion and the non-inverting input terminal voltage is the current value flowing through the I / V conversion resistor 3. Since there is no need to connect a circuit element requiring a bias current, such as a buffer amplifier or an arithmetic circuit, in addition to the current on / off semiconductor switch 23 to the path of the input current I, the measurement error caused by them is reduced. It does not occur.
In other words, this current / voltage conversion circuit is effective not only for range switching for a large current but also for a relatively small current.

FIG. 22 shows another basic circuit example of the number of ranges 1 of the multiplexed current / voltage conversion circuit according to claim 11 of the present invention.
FIG. 22 is obtained by replacing the current on / off semiconductor switch 23 of FIG. 21 with a diode switch 6, and the range switching operation is the same as that of the fourteenth embodiment, so that the description thereof is omitted.
When the range on / off switch circuit 120 is turned off, V12 becomes 0 V, the potential across the diode switch also becomes 0 V, and there is an advantage that the leakage current is reduced and the on / off control becomes unnecessary.

FIG. 23 shows still another basic circuit example of the range number 1 of the multiplexed current / voltage conversion circuit according to claim 11 of the present invention.
The difference from the output of the operational amplifier 12 for current / voltage conversion is taken with the output of the error amplifier 1 as a reference.
Since the range switching operation is the same as that of the fourteenth embodiment, the description is omitted.

When the range on / off switch circuit 120 is on, if the on-resistance value is sufficiently smaller than the resistance value R2 of the resistor 33 and can be ignored, V0≈V12. Therefore, in this circuit, the current value can be obtained by the equation (21). Can do.
This has the advantage that the number of circuits can be reduced because only one buffer amplifier 10 is required even if the number of ranges increases.

FIG. 24 shows still another embodiment of the range number 1 of the basic circuit of the multiplexed current / voltage conversion circuit according to claim 11 of the present invention.
The difference between the output V11 of the operational amplifier 12 for current / voltage conversion and the non-inverting input terminal potential V12 in FIG. 21 is stopped, and the current value I is directly calculated by V11.
Since the range switching operation is the same as that of the fourteenth embodiment, the description is omitted.

When the on / off semiconductor switch 23 has a sufficiently small on-resistance like the FET switch and the voltage drop due to the input current I becomes almost 0V, the inverting input terminal potential V12 of the operational amplifier 12 for current / voltage conversion is 0V. Can be considered
I = (V11−V12) / R1
≒ V11 / R1 (22)
Thus, the current value I can be directly calculated from the output voltage V11.
This has the advantage of reducing the circuit.

FIG. 25 is a circuit example of a current / voltage conversion circuit according to claim 12 of the present invention.
The circuit is the same as that of FIG. 22, but a current / voltage conversion circuit is provided for discharging current and for sucking current, respectively.
Since the range switching operation is the same as that of the fourteenth embodiment, the description is omitted.
The input current value I is the same as in Example 14. I = V1P / R1 + V1N / R1 (23)
Is required.
Normally, since either of the diode switches 6 and 6A is turned off, at least one of V1P and V1N in the equation (23) is 0V.

The switch circuit 130 for range ON / OFF enables reverse bias voltage application to the diode switches 6 and 6A when OFF, and is ON / OFF controlled by a range ON / OFF control signal that is an output of the arithmetic circuit 2. As long as analog signals such as analog switches, photo moss relays, FETs, transistors, mechanical relays can be turned on / off, general switch elements may be used, and a constant voltage source for setting a reverse bias voltage may be used.
Another circuit example of the switch circuit 130 is shown in FIG. The operation is the same as that of FIG. 43 and FIG. 46 described above, and will not be described.

  As in the case of claim 1, when it is desired to apply a reverse bias voltage in order to prevent a leakage current due to an offset voltage of the peripheral circuits of the diode switches 6 and 6A, reverse bias voltages −E1 and + E2 that can cancel the maximum expected offset voltage are set. When the switch circuit 130 is set, the reverse bias voltage is applied to the non-inverting input terminals of the operational amplifiers 12 and 12A for I / V conversion when the switch circuit 130 is off, and the inverting input terminals are also controlled to have the same potential. As a result, the diode switches 6 and 6A are reverse-biased to a required voltage.

  It is a feature and advantage of this circuit that it is not necessary to connect a circuit element requiring a bias current to the signal current path, and a reverse bias voltage can be applied with a simple circuit.

FIG. 26 is a circuit example of a multiplexed current / voltage conversion circuit according to claim 13 of the present invention.
This circuit is an extension of the circuit of FIG. Similarly, it can be expanded to any number of ranges.
Since the range switching operation is the same as in FIG. 21, the description of the operation is omitted.
The input current I is obtained by the sum of the current values of each range. In this example, I = V1 / R1 + V2 / R2 (24)
It is.
Since only one of the ranges is normally turned on, the range to be turned off among V1 and V2 in the equation (24) is 0V.

The resistor 14 and the switch 15 are for preventing the output of the negative feedback loop of the operational amplifier 1 from being opened and saturating the output when both the range 1 and the range 2 are turned off.
The input protection circuit 16 is a protection circuit for bypassing an excessive input or a current input when the entire range is off, and is not essential because it does not relate to the measurement function.

Each range can be arbitrarily turned on / off by the arithmetic circuit 2 using the range on / off control signal. Therefore, the current is automatically calculated using the current values obtained from the V / V or V1, V2 I / V conversion signals. You can change the range.
As an example, the flowchart of FIGS. 70 and 71 shows the procedure of range switching when the input current increases to 110% FS (full scale) and shifts to the upper range, and when the input current decreases to 9% FS to the lower range.
FIG. 70 shows a case where an overlap time for turning on both ranges at the time of range switching is provided, and FIG. 71 shows a case where the overlap time is unnecessary, and either one may be appropriately selected when applying.

  The feature of this circuit is that it is easy to extend the number of ranges and easily turn on / off any range, and it is not necessary to connect a circuit element that requires a bias current to the path of the input current. .

FIG. 27 shows another example of the multiplexed current / voltage conversion circuit according to claim 13 of the present invention, in which an I / V conversion resistor 17 having a resistance value R0 is added to the current / voltage conversion circuit of FIG. .
One range can be easily added by directly connecting the I / V conversion resistor 17 to the operational amplifier 1, and the current value of that range when all other ranges are turned off is obtained by V0 / R0.
Since the range switching operation is the same as in FIG. 26, the description of the operation is omitted.

FIG. 28 shows still another circuit example of the multiplexed current / voltage conversion circuit according to the thirteenth aspect of the present invention. The multiplexed current / voltage conversion circuit in the case where a difference is obtained for each range based on the output of the error amplifier 1. This is an example.
Since the range switching operation is the same as that of the nineteenth embodiment, the description of the operation is omitted.
When the ON resistance value of the range ON / OFF switch circuit 120 is sufficiently smaller than the resistance value R3 of the resistor 33 and can be ignored, V0≈V12, and the ON resistance value of the range ON / OFF switch circuit 120A is the resistance value R3A of the resistor 33A. When it is sufficiently small and can be ignored, V0≈V222, so that the current value can also be obtained from the equation (24) in this circuit.

FIG. 29 shows still another circuit example of the multiplexed current / voltage conversion circuit according to the thirteenth aspect of the present invention, which is an embodiment of the multiplexed current / voltage conversion circuit in which the difference calculation is unnecessary.
When the current on / off semiconductor switch 23 has a sufficiently small on-resistance like the FET switch and the voltage drop due to the current I1 becomes almost 0V, the inverting input terminal potential of the operational amplifier 12 for current / voltage conversion is V12≈0V. When the current on / off semiconductor switch 25 has a sufficiently small on-resistance like the FET switch and the voltage drop due to the current I2 becomes almost 0 V, the potential of the inverting input terminal of the operational amplifier 13 for current / voltage conversion Can be regarded as V22≈0V, so that the output voltage of the operational amplifier 12 is V11 and the output voltage of the operational amplifier 13 is V21. I = (V11−V12) / R1 + (V21−V22) / R2
= V11 / R1 + V21 / R2 (25)
Can directly calculate the current value I, which has the advantage of reducing the number of circuits.
Since only one of the ranges is normally turned on, the range to be turned off among V11 and V21 in the equation (25) is 0V.

FIG. 30 is a circuit example of a multiplexed current / voltage conversion circuit according to claim 14 of the present invention. In the circuit of FIG. 26, diode switches 6 and 7 are used as current on / off switches, and resistance values R11 and R21 are set. In this case, resistors 18 and 19 are inserted, and no dead zone circuit is provided between the operational amplifier 1 and the switch circuits 120 and 120A.
The relationship between the input current I and the output voltage V0 of the operational amplifier 1 when sequentially turning on only one range without R11 and R21 is as shown in FIG. 66, and the maximum value of V0. Is almost the same as the voltage across the diode switches 6 and 7 and is non-linear and highly temperature-dependent, with a maximum variation of typically ± 0.8 to 1.2 V, and the output voltage V0 of the operational amplifier 1 is switched over. It is difficult to set the calculation condition as follows.
However, FIG. 66 shows a case where the number of ranges is expanded to n.

On the other hand, when resistors R11 and R21 are inserted as shown in FIG. 30 and no dead zone circuit is provided between the operational amplifier 1 and the switch circuits 120 and 120A, only one of the ranges is turned on, and the switches are sequentially turned on from the minimum range. In this case, the relationship between the input current I and the output voltage V0 of the operational amplifier 1 is as shown in FIG. However, FIG. 67 shows a case where the number of ranges is expanded to n.
When only range 1 is on, the inverting input terminal potential V12 of the I / V conversion operational amplifier 12 is equal to the non-inverting input terminal potential and thus becomes V0. Therefore, when the voltage between both terminals of the diode switch is VF1,
V0 = V12
= VF1 + R11 · I (26)
If R11 is set appropriately and VF1 is made relatively small with respect to R11 · I, the relationship between V0 and input current I becomes a stable proportional relationship, and the same applies to other ranges, so V0 is calculated. It is a feature and an advantage that it can be used for the calculation conditions of the circuit 2.

FIG. 31 is another circuit example of the current / voltage conversion circuit according to the fourteenth aspect of the present invention, and is provided between the non-inverting input terminals of the operational amplifier 1 and the I / V conversion operational amplifiers 12 and 13 in the circuit of FIG. Switch circuits 140 and 140A having dead zone circuits are provided. FIG. 48 shows an example of switch circuits 140 and 140A.
141 is a known dead zone circuit, 143 and 144 are constant voltage sources for dead zone setting voltage, and 142 is an inverting amplifier.

The on / off control 140 is performed by the Vcont input voltage, and the operation is the same as in FIG.
140 circuit function Vout = db (Vin, Edb, Vcont) (27)
It shall be indicated by
However, when Vcont = 0V, use the equation (1). Vout = db (Vin, Edb) (28)
When Vcont = Vdis,
Vout = 0V (29)
And

  Here, the dead band setting voltage Edb1 of the minimum range 1 is set to 0V, the dead band setting voltage of the range 2 is Edb2 in which the input current when the range 1 is on is equal to the value V0 when the full scale value I1FS, and the dead band setting voltage every time the range increases. Is set to be equal to V0 when the input current when the range is smaller by one range becomes a full scale value.

In this case, if there is no R11, R21, the dead band setting voltage Edb2 of the range 2 may be set to the maximum value VF1 of the potential difference between both ends of the diode switch 6. Edb2 = VF1
The same applies to range 3 and beyond. Edb3 = Edb2 + VF2 (30)
:
The relationship between the input current I and the output voltage V0 of the operational amplifier 1 when sequentially turning on only one range under the conditions is as shown in FIG. The change width is almost the voltage across the diode switch, is nonlinear and has high temperature dependence, and usually has a large variation of ± 0.8 to 1.2 V at the maximum, making it difficult to make V0 a calculation condition such as range switching. It is.
However, FIG. 68 shows a case where the number of ranges is expanded to n.

On the other hand, when resistors R11 and R21 are inserted as shown in FIG. 31 and a dead zone circuit is provided in the switch circuits 140 and 140A, if the dead zone set voltage is set according to the above principle,
Edb1 = 0V (31)
Edb2 = Edb1 + R11 · I1FS + VF1 (32)
Edb3 = Edb2 + R21 · I2FS + VF2 (33)
:
It becomes. At this time, when only one of the ranges is turned on, the relationship between the input current I and the output voltage V0 of the operational amplifier 1 when sequentially turning on from the minimum range is a polygonal monotonically increasing relationship as shown in FIG. .
However, FIG. 69 shows a case where the number of ranges is expanded to n.

When only range 1 is on, the inverting input terminal potential of the operational amplifier 12 for I / V conversion is equal to the non-inverting input terminal potential V12, so that the potential difference across the diode switch 6 is VF1.
V0 = V12 + Edb1
= VF1 + R11 · I + Edb1 (34)
If R11 is set appropriately and VF1 is made relatively small relative to R11 · I, the relationship between V0 and input current I becomes a stable proportional relationship with Edb1 as an offset, and the same applies to other ranges. Therefore, V0 can be used as a calculation condition of the calculation circuit 2 and is advantageous.

  FIG. 32 is a basic circuit example of a multiplexed current / voltage conversion circuit using a VCR switch according to claim 15 of the present invention, in which the semiconductor switch 23 and the switch circuit 120 of FIG. 24 are replaced with VCR switches 400 and 400A. The range switching operation is the same as in FIG.

  If the resistance and capacitor (not shown) of the integration circuit in the VCR switches 400 and 400A are appropriately selected so that the change in the resistance value of the switch at the time of on / off becomes a speed at which the response of the negative feedback circuit can follow. It is a feature and advantage that a multiplexed current / voltage conversion circuit with less spike noise of the operational amplifiers 1 and 12 at the time of range switching can be obtained.

  FIG. 33 shows another example of the multiplexed current / voltage conversion circuit using the VCR switch according to the fifteenth aspect of the present invention. The semiconductor switches 23 and 25 and the switch circuits 120 and 120A of FIG. 29 are replaced with the VCR switches 400, 400A and 400B. , 400C, and the range switching operation is the same as in FIG.

  The resistance of the integrating circuit and the capacitor (not shown) in the VCR switches 400, 400A, 400B, and 400C are appropriately selected, and the change in the resistance value of the switch at the time of ON / OFF becomes the speed that the response of the negative feedback circuit can follow. In this way, it is possible to obtain a multiplexed current / voltage conversion circuit with less spike noise of the operational amplifiers 1, 12, 13 at the time of range switching, which is advantageous.

FIG. 34 shows an embodiment in which a phase compensation capacitor is provided for each range of the multiplexed current / voltage conversion circuit according to claim 16 of the present invention, and since the range switching operation has been described, description thereof will be omitted.
In general, a current / voltage conversion circuit using an operational amplifier often requires a phase compensation capacitor to prevent oscillation of the operational amplifier, and is also required for a multiplexed current / voltage conversion circuit.

  As shown in FIG. 35, the phase compensation capacitor 29 may be inserted between the inverting input terminal and the output terminal of the operational amplifier 1, but in this case, since the capacitance CF of the capacitor is common to each range, it is necessary for each range. However, there is a drawback that it is necessary to make it the largest value and unnecessarily slow the response to a range that requires a smaller value.

  On the other hand, in the case of FIG. 34, a capacitor having an optimum value for each range is connected to the non-inverting input terminal of the operational amplifier for I / V conversion and the operational amplifier 1 of the semiconductor switch for current on / off for each range. It is connected between the terminals connected to the input terminals, and the capacitor 30 with the capacity CF1 in the range 1 and the capacitor 31 with the capacity CF2 in the range 2 are optimum values.

When range 1 is off, the non-inverting input terminal potential V12 of the operational amplifier 12 for I / V conversion is 0V, and the voltage between both terminals of the capacitor 30 is 0V, which is equivalent to the absence of the capacitor 30. When range 2 is off, the voltage between both terminals of the capacitor 31 is 0V, which is equivalent to the absence of the capacitor 31.
As a result, since the capacitors 30 and 31 are turned off when the range is turned off, there is a feature and advantage that there is no adverse effect such as causing a response delay of the circuit or generating a leakage current.

  FIG. 36 is a circuit example of the resistance series current / voltage conversion circuit 1 using the VCR switch according to claim 17 of the present invention, and the range switching operation is the same as that of FIG.

  If the resistance and capacitor (not shown) of the integration circuit in the VCR switches 400 and 400A are appropriately selected so that the change in the resistance value of the switch at the time of ON / OFF becomes a speed at which the response of the negative feedback circuit can follow. It is a feature and advantage that a resistance series current / voltage conversion circuit 1 with less spike noise of the operational amplifier 1 at the time of range switching can be obtained.

  FIG. 37 shows another circuit example of the resistance series current / voltage conversion circuit 1 using the VCR switch according to claim 17 of the present invention. The dead zone circuits 39 and 40 are added to the circuit of FIG. Since this is the same as described above, the description is omitted.

  If the resistance and capacitor (not shown) of the integration circuit in the VCR switches 400 and 400A are appropriately selected so that the change in the resistance value of the switch at the time of ON / OFF becomes a speed at which the response of the negative feedback circuit can follow. In addition to being able to obtain the resistance series current / voltage conversion circuit 1 with less spike noise of the operational amplifier 1 when the range is switched, the dead band circuits 39 and 40 can change the output voltage V1 of the operational amplifier 1 when the range is switched. It is small and has the advantage of shortening the settling time.

  FIG. 38 shows still another circuit example of the resistor series current / voltage conversion circuit 1 using the VCR switch according to the seventeenth aspect of the present invention. The range switching operation is the same as that of FIG.

  The resistance of the integrating circuit and the capacitor (not shown) in the VCR switches 400, 400A, 400B, and 400C are appropriately selected, and the change in the resistance value of the switch at the time of ON / OFF becomes the speed that the response of the negative feedback circuit can follow. In this way, the resistance series current / voltage conversion circuit 1 with less spike noise of the operational amplifier 1 at the time of range switching can be obtained, which is advantageous.

FIG. 39 is a circuit example of a current / voltage conversion circuit according to claim 18 of the present invention, which is a combination of a multiplexed current / voltage conversion circuit and a resistor series current / voltage conversion circuit.
The resistor 3 is an I / V conversion resistor for a range 1 having a resistance value R1, the resistor 153 is an I / V conversion resistor for a range 2 having a resistance value R2, and the resistor 154 is an I / V conversion resistor for a range 3 having a resistance value R3. / V conversion resistor, range 1 is a multiplexed current / voltage conversion circuit according to claim 13, and range 2 and range 3 are configured by a known resistance series current / voltage conversion circuit 150.

When the potential difference of the I / V conversion resistance of the resistance series current / voltage conversion circuit 150 is obtained, the comparison reference potential is normally the potential of the inverting input terminal of the operational amplifier 152, but in this circuit example, it is the same potential. By inputting to the arithmetic circuit 2 from the non-inverting input terminal via the buffer amplifier 151, the measurement accuracy deterioration due to the bias current of the buffer amplifier 151 is eliminated.
On / off control of each range is performed by controlling the range 1 on / off control signal, the range 2, 3 on / off control signal, and the range 3 on / off control signal by the arithmetic circuit 2.
The diode switches 6 and 7 may be VCR switches or FET switches.

The operations of the multiplexed current / voltage conversion circuit and the resistor series current / voltage conversion circuit are as described above. The outline of the circuit operation when combining them will be described below.
When using this circuit, it is assumed that both the switch circuits 120 and 120A are controlled so that there is no period during which the negative feedback loop of the operational amplifier 1 is not opened.

The output of the operational amplifier 152 is controlled so that the potential of the inverting input terminal becomes equal to the non-inverting input terminal to which the output voltage of the switch circuit 120A is applied.
Therefore, when the range 2, 3 on / off control signal is off, the potential of the non-inverting input terminal of the operational amplifier 152 is 0V, the inverting input terminal is also 0V, and the voltage between both terminals of the diode switch 7 is also 0V. The series current / voltage conversion circuit 150 is turned off.

When the range 2, 3 on / off control signal is turned on, the potential at the right terminal of the diode switch 7 becomes V0, the resistance series current / voltage conversion circuit 150 is turned on, and if the range 3 on / off control signal is off, the range is turned on. If 2 is valid and on, range 3 is valid.
Either one of Range 1 and Range 2 or Range 3 may be on or both, and the current value I is when Range 3 is off. I = V1 / R1 + V2 / (R2 + R3) (35)
When range 3 is on, I = V1 / R1 + V3 / R3 (36)
It can be obtained by the operation of

In this circuit, when the range 2, 3 on / off control signal is turned off, the resistance series current / voltage conversion circuit 150 is turned off and disconnected from the range 1 by the diode switch 7, so that the buffer amplifier on the resistance series current / voltage conversion circuit 150 side. In addition, there is an advantage that an error factor caused by a bias current of an element used in the arithmetic circuit 2 does not easily affect the range 1 side which is a small current range.
Note that the number of ranges can be arbitrarily increased with the same configuration as in this circuit example.

  As described above, the small current range in which the influence on the measured value of the bias current of the buffer amplifier, the arithmetic circuit, etc. cannot be ignored is constituted by the multiplexed current / voltage conversion circuit according to claim 13, claim 14, or claim 15. For non-existing ranges, elements are used in a relatively small circuit even with a large number of ranges by being configured with the resistor series current / voltage conversion circuit of claim 1 or claim 2 or claim 3 or claim 4 or claim 17. It is a feature and advantage of this circuit example that an arbitrary range on / off controllable current / voltage conversion circuit that is less affected by the leakage current and bias current and can be controlled with high accuracy can be obtained.

The same effect can be obtained by replacing the resistance series current / voltage conversion circuit 150 of FIG. 39 with the resistance parallel current / voltage conversion circuit according to claim 5 or 10 and combining with the multiplexed current / voltage conversion circuit. (Not shown)

When the range switching circuit of the present invention is used, it is possible to obtain a current / voltage conversion circuit with little measurement error due to bias current or offset voltage of an operational amplifier, a buffer amplifier, or the like.
Further, according to the resistance parallel current / voltage conversion circuit or the multiplexed current / voltage conversion circuit of the present invention, the current / current with little measurement error due to the leakage current of the semiconductor switch, the bias current of the operational amplifier and the buffer amplifier, and the offset voltage. A voltage conversion circuit can be obtained.
Further, when the VCR switch circuit of the present invention is used, a current / voltage conversion circuit with less spike noise at the time of range switching can be obtained.
Similarly, when the VCR switch circuit of the present invention is used for a switch of a general negative feedback circuit having a circuit changeover switch, a negative feedback circuit with less spike noise at the time of switch change can be obtained.

It is an Example of the resistance series current / voltage conversion circuit which has the current drive circuit with a reverse bias of this invention. It is an Example of the resistance series current / voltage conversion circuit which has the current drive circuit with a reverse bias which has the range control part divided into positive and negative of this invention. It is an Example of the current / voltage conversion circuit which arranged the I / V conversion resistance which has the current drive circuit with a reverse bias of this invention in parallel. It is an Example of the resistance series current / voltage conversion circuit which has a diode switch with a reverse bias application circuit of this invention. It is an Example of the resistance series current / voltage conversion circuit which made unnecessary the voltage conditions of the diode switch by the side of the I / V conversion resistance of the present invention at the time of range off. It is an Example of the resistance series current / voltage conversion circuit 2 which enabled / disabled control of the range switching function of this invention. It is a basic circuit example of the resistance parallel current / voltage conversion circuit of the present invention. The basic circuit of the resistance parallel current / voltage conversion circuit according to the present invention is in a state where range 1 is on and range 2 is off. It is a basic circuit in the case of using the differential operation of the resistance parallel current / voltage conversion circuit of the present invention. It is a circuit example of the VCR switch by NJ-FET. In this example, the number of diodes is reduced and the parallel resistance value of R1 and R2X is used. In this example, the number of diodes is reduced and the parallel resistance value of R1X and R2 is used. It is a circuit example of the VCR switch by NJ-FET using the level conversion circuit of this invention. In this example, the number of diodes is reduced and the parallel resistance value of R1 and R2X is used. In this example, the number of diodes is reduced and the parallel resistance value of R1X and R2 is used. 4 is a time chart of a gate on / off control signal V1 and a gate control circuit output voltage V2. This is an example in which the input resistance of the negative feedback circuit is switched by a VCR switch. This is a replacement of a switch connected in series with a resistor with a VCR switch. This is a replacement of a switch connected in parallel with a resistor with a VCR switch. It is a basic circuit of a resistance parallel current / voltage conversion circuit using the VCR switch of the present invention. It is an example of a basic circuit of the multiplexed current / voltage conversion circuit of the present invention. 1 is a basic circuit of a multiplexed current / voltage conversion circuit using a diode switch of the present invention. This is a basic circuit of a multiplexed current / voltage conversion circuit in the case where the difference from the output of the operational amplifier for current / voltage conversion is taken with reference to the output of the error amplifier. This is a basic circuit of a multiplexed current / voltage conversion circuit when the output of the operational amplifier for current / voltage conversion is directly used as a current detection signal. It is an example of a basic circuit of a multiplexed current / voltage conversion circuit capable of applying a reverse bias voltage to the diode switch of the present invention. 2 is an example of a multiplexed current / voltage conversion circuit of the present invention. It is an example of a multiplexed current / voltage conversion circuit in which an I / V conversion resistor R0 is connected to the operational amplifier for error amplification of the present invention. It is an example of a multiplexed current / voltage conversion circuit when a difference is taken for each range with reference to the output of the error amplifier of the present invention. It is an example of a multiplexed current / voltage conversion circuit that does not require differential calculation according to the present invention. It is an example of a multiplexed current / voltage conversion circuit in which a resistor is connected to the diode switch of the present invention. It is an example of the multiplexed current / voltage conversion circuit using the series resistance of the diode switch of this invention, and a dead zone circuit. It is a basic circuit example of the multiplexed current / voltage conversion circuit by the VCR switch of the present invention. It is a circuit example in the case of the number of ranges of 2 of the multiplexing current / voltage conversion circuit by the VCR switch of this invention. This is an embodiment in which a phase compensation capacitor is provided for each range of the multiplexed current / voltage conversion circuit of the present invention. This is an embodiment in which the phase compensation capacitor of the multiplexed current / voltage conversion circuit is shared. It is a circuit example of the resistance series current / voltage conversion circuit 1 by the VCR switch of this invention. It is a circuit example of the resistance series current / voltage conversion circuit 1 by the VCR switch and dead zone circuit of this invention. It is a circuit example of the resistance series current / voltage conversion circuit 1 by the VCR switch of this invention. It is an example of the current / voltage conversion circuit which combined the multiplexed current / voltage conversion circuit of this invention, and the resistance series current / voltage conversion circuit. It is a block diagram of the resistance series current / voltage conversion circuit 1 using the disclosed switch. It is a block diagram of the resistance series current / voltage conversion circuit 2 using the disclosed dead zone circuit and limit circuit. It is the block diagram which expressed collectively the resistance series current / voltage conversion circuit 1 and resistance series current / voltage conversion circuit 2 which were already disclosed. It is a circuit example of the current drive circuit with a reverse bias. It is a circuit example of the current drive circuit with a reverse bias which divided the range control part and the current drive circuit into positive and negative. It is a circuit example of the range switching circuit in which enable / disable control is possible. It is an example of a circuit of the switch part of a range switching circuit. It is an example of a reverse bias application circuit. It is an example of a dead zone circuit in which enable / disable control is possible. It is an input-output characteristic figure of a dead zone circuit. It is an example of a dead zone circuit by a Zener diode. It is an example of a known dead zone circuit. This is an example of a known addition / subtraction circuit. This is an inverting amplifier circuit for switching an input resistance using a known negative feedback. This is an inverting amplifier circuit for switching a negative feedback resistor using a known negative feedback. This is a known constant voltage / constant current generation circuit using negative feedback. This is a constant current generation circuit using a known negative feedback. This is a voltage application circuit using a known negative feedback. It is a constant voltage generation circuit with a current measuring unit using a known negative feedback. This is a known range / switchable current / voltage conversion circuit. It is the schematic of the voltage-current characteristic of a general diode. It is an example of the characteristic voltage-current characteristic of the diode switch connected bidirectionally in parallel. This is a connection example in which MOS-FETs are serially connected in the reverse direction to make them bidirectional. It is a connection example of a photo moss relay. It is an example of the characteristic of gate-source voltage Vgs and drain-source resistance Rds of NJ-FET. It is a Vds-Ids characteristic example at the time of OFF of NJ-FET. It is an input current-operation amplifier output voltage relationship diagram at the time of ON control only for one range of the multiplexed current / voltage conversion circuit by the range switching circuit without resistance and dead zone. It is an input current-operational amplifier output voltage relationship diagram at the time of ON control for only one range of a multiplexed current / voltage conversion circuit using a range switching circuit with resistance and no dead zone. It is an input current-operation amplifier output voltage relationship diagram at the time of ON control for only one range of a multiplexed current / voltage conversion circuit using a range switching circuit with no resistance and a dead zone. FIG. 5 is a relationship diagram of an input current and an operational amplifier output voltage when only one range of a multiplexed current / voltage conversion circuit using a range switching circuit with a resistance and a dead zone is on-controlled. It is a flowchart of the example of a range switching control procedure in consideration of the range on delay time. It is a flowchart of the example of a range switch control procedure which does not consider range on delay time.

Explanation of symbols

1, 12, 12A, 13, 152, 301, 421 Operational amplifier 2 Operation circuit 3, 3A, 4, 5, 17, 153, 154 I / V conversion resistor 6, 6A, 7, 7A, 73, 74 Diode switch 8 9, 10, 10A, 11, 151, 152 Buffer amplifiers 14, 18, 19, 33, 34, 37, 38, 75, 76, 304,
305, 306, 307, 402, 422, 423, 424, 425,
426, 433, 441, 442 Resistance 15, 91, 91A, 310, 311 Switch 16 Input protection circuit 20, 20A, 21, 22, 308 Differential amplifier 23, 24, 25, 26 Semiconductor switch 27, 28 Inverter 29, 30 , 31, 422, 427, 445 capacitors 35, 36, 52, 53, 62, 63, 82, 92, 92A, 104,
104A, 118 Current drive circuit 50, 50A, 60, 80, 90, 90A, 100, 100A,
110, 110A, 110 Range switching circuit 51, 61, 68, 69, 81 Range controller 32, 54, 55, 64, 65 Current booster 56, 57, 66, 67, 71, 72, 114, 115, 116,
117, 131, 132, 143, 144 Constant voltage source 70 Reverse bias application circuit 73, 74, 403, 428, 429, 443, 444 Diode 39, 40, 93, 93A, 101, 101A, 111, 121,
141 Dead band circuit 102, 102A, 112 Limit circuit 103, 103A Adder 113, 122, 133, 142 Inverting amplifier 120, 120A, 130, 140, 140A Switch circuit
150 Resistance Series Current / Voltage Conversion Circuit 302, 303 Load 309 Current Measurement Unit 400, 400A, 400B, 400C VCR Switch 401 N-Channel Junction FET
420 level conversion circuit 430 level conversion unit 431 NPN transistor 432 PNP transistor 440 CR integration circuit

Claims (18)

  It has an operational amplifier and a plurality of I / V conversion resistors connected in series or in parallel. A diode switch and a current drive circuit are provided at one end of each I / V conversion resistor, and the current switching circuit is turned on / off by the range switching circuit. In a current / voltage conversion circuit that performs range switching, a diode switch and a current drive circuit configured to apply a reverse bias voltage to the diode switch when the range is off are provided separately for current discharge and current sink. Range switching circuit characterized by reducing measurement error due to leakage current of diode switch.   It has an operational amplifier and a plurality of I / V conversion resistors connected in series or in parallel. A diode switch and a current drive circuit are provided at one end of each I / V conversion resistor, and the current switching circuit is turned on / off by the range switching circuit. In the current / voltage conversion circuit that switches the range, a diode switch with a circuit that applies a reverse bias voltage when the range is off is provided separately for the current discharge direction and the current suction direction, and the leakage current of the diode switch A range switching circuit characterized by reducing measurement errors caused by.   3. A current / voltage conversion circuit using the range switching circuit according to claim 1 or 2, wherein a reverse bias having a magnitude in which a diode switch of the range is reverse biased with respect to a current input when the range is turned on. A range switching circuit characterized in that the voltage is set in the range switching circuit and the input of the terminal potential on the I / V conversion resistance side of the diode switch to the range switching circuit is unnecessary.   It has an operational amplifier and a plurality of I / V conversion resistors connected in series. A diode switch and a current drive circuit are provided for each I / V conversion resistor other than the minimum range. In the current / voltage conversion circuit called the resistor series current / voltage conversion circuit 2 that operates, the dead zone circuit and limit circuit are provided with external voltage input sections, and the dead zone set voltage and limit set voltage are changed by the voltage applied to these. A range switching circuit characterized in that the range on / off operation can be forcibly enabled / disabled.   Connects one end of a current on / off switch using a semiconductor switch and one end of an I / V conversion resistor, and provides a T-shaped circuit with a ground connection switch using an FET switch or an analog switch for the required number of ranges. Are connected to the inverting input terminal of the operational amplifier, and the I / V of each T-shaped circuit is connected to the inverting input terminal of the operational amplifier. Connect the terminal on the opposite side of the conversion resistor's ground connection switch to the output terminal of the operational amplifier. For the range to be turned on, turn on the current on / off switch and turn off the ground connection switch. Measures due to the leakage current of the semiconductor switch by turning off the current on / off switch and turning on the ground connection switch. Current / voltage conversion circuit called a resistor parallel current / voltage conversion circuit, characterized in that with reduced differences.   The FET switch is configured to gradually decrease / increase the gate control voltage or current with an arbitrary time constant with respect to the ON / OFF control signal of the FET switch by the integration circuit composed of a resistor, a capacitor and a diode as necessary. A switch circuit characterized in that the resistance value between the drain and the source is gradually reduced / increased.   An integration circuit is configured by combining a resistor, a capacitor and, if necessary, a diode with an operational amplifier. A predetermined reference voltage is applied to the non-inverting input terminal of the operational amplifier, and an on / off input signal of an arbitrary voltage is applied. A level conversion circuit characterized in that the time constant of the output voltage and the voltage at settling can be set arbitrarily.   The level conversion circuit according to claim 7 is used to gradually decrease / increase the gate control voltage or current at an arbitrary time constant with respect to on / off of an arbitrary voltage on / off control signal, and to set the voltage or current at the time of settling. A switch circuit characterized in that the resistance value between the drain and source of an FET switch is gradually reduced / increased and the dead time of on / off operation can be reduced by setting to an arbitrary value.   Negative using an operational amplifier circuit having one or any of a plurality of input resistors and their selection switches, or a plurality of negative feedback resistors and their selection switches, or a plurality of load circuits and their selection switches In the feedback circuit, the switch circuit according to claim 6 or 8 is used as the selection switch, and the time constant of the switch circuit is set so that the change in the resistance value of the switch at the time of ON / OFF becomes a speed that can follow the response of the negative feedback circuit A negative feedback circuit characterized by reducing spike noise in the operational amplifier that occurs when the switch circuit is turned on / off.   The switch circuit according to claim 6 or claim 8 is used as a switch of the resistor parallel current / voltage conversion circuit according to claim 5, and the change in the resistance value of the switch at the time of ON / OFF becomes a speed at which the response of the negative feedback circuit can follow. The current / voltage conversion circuit is characterized in that the time constant of the switch circuit is set in the same way, and the spike noise of the operational amplifier generated when the switch circuit for range switching is turned on / off is reduced.   An operational amplifier for error amplification and an operational amplifier for I / V conversion using an I / V conversion resistor as a negative feedback resistor are provided, and one terminal of a current on / off semiconductor switch is used as an inverting input terminal of the operational amplifier for error amplification. The other terminal is connected to the inverting input terminal of the operational amplifier for I / V conversion, and the connection destination of the non-inverting input terminal of the operational amplifier for I / V conversion is operated for error amplification by a semiconductor switch for range on / off. By making it possible to select the amplifier output or ground, and by turning on / off the semiconductor switch for current on / off and / or the semiconductor switch for range on / off, the leakage current of the semiconductor switch is reduced. ON / OFF control of the current flowing through the / V conversion resistor is possible, and the potential difference between the output voltage of the I / V conversion operational amplifier and the non-inverting input terminal voltage flows through the I / V conversion resistor. Current / voltage conversion circuit characterized by comprising a voltage proportional to the current value.   12. The current / voltage conversion circuit according to claim 11, wherein a diode switch is used as a semiconductor switch for current on / off, wherein the diode switch, the I / V conversion resistor, and the I / V conversion operational amplifier are used for current discharge and current sink. A current / voltage conversion circuit characterized in that a reverse bias voltage value to be applied when each diode switch is turned off is applied to a non-inverting input terminal of an operational amplifier for I / V conversion to suppress a leakage current of the diode switch.   A circuit for I / V conversion for each range of the current / voltage conversion circuit according to claim 11 or 12 is provided in parallel for the required number of ranges, and this is combined with an operational amplifier for error amplification to reduce the leakage current of the semiconductor switch. A current / voltage conversion circuit called a multiplexed current / voltage conversion circuit characterized in that an arbitrary range can be controlled on / off.   14. The multiplexed current / voltage conversion circuit according to claim 13, wherein a resistor is inserted between the semiconductor switch for current on / off and the inverting input terminal of the operational amplifier for I / V conversion, and the semiconductor for range on / off as required. A current / voltage conversion circuit characterized in that a dead band circuit is provided between the switch and the output terminal of the error amplification operational amplifier to widen the output voltage range of the error amplification operational amplifier.   15. The multiplexed current / voltage conversion circuit according to claim 11 or claim 12, or claim 13 or claim 14, wherein the current on / off semiconductor switch and the range on / off semiconductor switch are constituted by FET switches. The switch circuit time constant is set so that the change of the resistance value of the switch at the time of ON / OFF becomes the speed that the response of the negative feedback circuit can follow, and each calculation accompanying the range switching A current / voltage conversion circuit characterized by reducing spike noise in the amplifier.   16. The multiplexed current / voltage conversion circuit according to claim 13, 14 or 15, wherein a phase compensation capacitor having an optimum value for each range is provided with a non-inverting input of an operational amplifier for I / V conversion for each range. A current / voltage conversion circuit characterized in that it is connected between a terminal and a terminal on the side connected to the inverting input terminal of an operational amplifier for error amplification of a semiconductor switch for current on / off.   It has an operational amplifier and a plurality of I / V conversion resistors connected in series. A diode switch and a current drive circuit are provided at one end of each I / V conversion resistor other than the minimum range, and the current switching circuit is turned on / off by the range switching circuit. In a current / voltage conversion circuit called a resistance series current / voltage conversion circuit 1 that is turned off and switches the range, the input of the current drive circuit is used as the detection voltage of the I / V conversion resistor of the range for switching the range, 9. The switch circuit according to claim 6 or 8 is used to select whether the output voltage of an operational amplifier for error amplification or a dead zone circuit provided at its output section is necessary. The time constant of the switch circuit was set so that the change could follow the response of the negative feedback circuit, and the spike noise of the operational amplifier due to range switching was reduced. Current / voltage conversion circuit according to claim.   Multiplexed current / voltage converter circuit according to claim 13 or claim 14 or claim 15 and any number of ranges of resistance series current / voltage converter circuit or claim 1 or claim 2 or claim 3 or claim Combined resistance series current / voltage conversion circuit according to claim 4 or claim 17, or any number of ranges of multiplexed current / voltage conversion circuit according to claim 13, claim 14 or claim 15, and any number of ranges of claim In combination with the resistance parallel current / voltage conversion circuit according to claim 5 or claim 10, the measurement error caused by the leakage current of the semiconductor switch, the bias current of the circuit elements used in the buffer amplifier, the operational amplifier, and other arithmetic circuits, or the offset voltage is reduced. A current / voltage conversion circuit characterized by a reduction.

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