JP2002231893A - Semiconductor integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor integrated circuit capable of externally varying current values, gains and frequency characteristics without refabricating a chip itself and utilizing a FIB or a laser cutter. SOLUTION: An N-channel MOS transistor 8 is switching-activated by externally controlling the gate voltage and is functioned as a resister element whose conductive resistance is varied by continuously controlling a conduction state between an on-state and an off-state so that it makes possible to externally control the current value of Iout in a reference constant current source circuit by varying a resistance value in a resistance circuit consisting of a resister 2 and a resister 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor integrated circuit by a process capable of forming a MOS transistor.

[0002]

2. Description of the Related Art In a conventional semiconductor integrated circuit, not a resistor but a constant current source is often used as a means or a load for applying a bias current. FIG. 4 is a circuit diagram illustrating an example of a constant current circuit that generates a constant current that is a reference necessary for the bias current circuit. This constant current circuit has a resistance of 1,
It is composed of a resistor 2, a transistor 3, and a transistor 4. The resistor 1 has one terminal 1a connected to a power supply voltage V of an external power supply.
cc, and the other terminal 1b is connected to the base of the transistor 3 and the collector of the transistor 4. The resistor 2 has one terminal 2 a connected to the emitter of the transistor 3 and the base of the transistor 4, and the other terminal 2 b grounded together with the emitter of the transistor 4.

Next, the operation will be described. The potential of the other terminal 1b of the resistor 1 is determined by the base-emitter voltage of the transistor 3 and the transistor 4, and a current flows with a potential difference from the power supply voltage Vcc of the external power supply, so that the transistors 3 and 4 are biased. The potential at one terminal 2 a of the resistor 2 is determined by the base-emitter voltage of the transistor 4. Voltage-current conversion is performed by the resistor 2 and the transistor 3, and a constant current is obtained as Ic. In this constant current circuit, the base-emitter voltage of the transistor is substantially a known constant value, and the current value of Ic is set by the resistance value of the resistor 2.

[0004]

Since the conventional semiconductor integrated circuit is constructed as described above, the chip area can be reduced by using a transistor while minimizing the use of a resistor, and the emitter-base of the transistor can be reduced. Determining the potential with the intermediate voltage has the advantage that the dependence of the current value on the power supply voltage fluctuation can be reduced. However, when changing the constant of each element of the circuit, such as adjusting the current value or the voltage value, it is necessary to remanufacture from the beginning,
Alternatively, a large-scale device such as a FIB (focused ion beam correction device) and a laser cutter is used to revise the mask, thereby increasing the cost and delivery time, and changing the constant of each element constituting the circuit. There was a problem that it could not be easily performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is possible to re-manufacture a chip itself, revise a mask, or use a current value and a gain without using an FIB or a laser cutter. It is another object of the present invention to provide a semiconductor integrated circuit in which the frequency characteristics can be easily adjusted and changed from the outside.

[0006]

A semiconductor integrated circuit according to the present invention has a passive resistance element and a constant current generation circuit whose current value is determined by the resistance value of the passive resistance element. A MOS transistor functioning as a resistance element connected in parallel to the passive resistance element, the gate potential of which is controlled from the outside, and its conduction state continuously changes between the on state and the off state to change the conduction resistance;
A current setting unit for varying the constant of a circuit including a passive resistance element by the gate potential of the S transistor to vary the current value of the constant current generation circuit, and for applying a gate voltage for applying a gate potential to the gate of the MOS transistor from the outside And a terminal.

A semiconductor integrated circuit according to the present invention is a semiconductor integrated circuit having an amplifying circuit having a passive resistance element and a gain determined by a resistance value of the passive resistance element,
A MOS that is connected in parallel to a passive resistance element and that functions as a resistance element whose gate potential is controlled from the outside and whose conduction state changes continuously between the ON state and the OFF state and the conduction resistance changes
A variable load resistor section having a transistor, and varying the constant of a circuit including a passive resistance element by the gate potential of the MOS transistor to vary the gain of the amplifier circuit; and a gate for externally applying a gate potential to the gate of the MOS transistor And a voltage application terminal.

A semiconductor integrated circuit according to the present invention is a semiconductor integrated circuit having a passive capacitance element and a filter circuit whose frequency characteristic is determined by the capacitance value of the passive capacitance element, wherein the filter circuit is connected in parallel to the passive capacitance element A MOS transistor which functions as a resistance element whose gate voltage is controlled from the outside and whose conduction state changes continuously between an on state and an off state and whose conduction resistance changes, and a passive capacitance element is provided by the gate potential of the MOS transistor. And a capacitance setting unit that varies the frequency characteristics of the filter circuit by varying the constant of the circuit including: and a gate voltage application terminal for externally applying a gate potential to the gate of the MOS transistor.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below. Embodiment 1 FIG. In the semiconductor integrated circuit of the first embodiment, a reference constant current generation circuit using a process capable of forming a MOS transistor will be described as an example.
FIG. 1 is a circuit diagram showing a configuration of a reference constant current generation circuit according to the first embodiment. Since the reference constant current generation circuit shown in FIG. 1 is formed as an integrated circuit, unlike the reference constant current generation circuit having a so-called discrete configuration in which resistance elements and transistors are arranged and mounted on a substrate, It is not possible to fine-tune or change the electrical characteristics by replacing the transistor. In the figure, 1, 2,
7 is a resistor (passive resistance element), 3 and 4 are NPN transistors, 5 is a power supply line of a power supply voltage Vcc, and 6 is a current output I
out line, 8 is an N-channel MOS transistor, 1
Reference numeral 0 denotes a current setting unit which includes the resistors 2 and 7 and the N-channel MOS transistor 8 and externally sets the current output Iout. 51 denotes a gate for applying a gate voltage to the gate of the N-channel MOS transistor 8 from outside the integrated circuit. This is a gate voltage application terminal.

[0010] Each element is connected as follows. The resistor 1 has one terminal 1a connected to the power supply line 5 of the power supply voltage Vcc, and the other terminal 1b connected to the transistor 3
And the collector of the transistor 4. The resistor 2 has one terminal 2 a connected to the emitter of the transistor 3 and the base of the transistor 4, and the other terminal 2 b connected to one terminal 7 a of the resistor 7. The other terminal 7b of the resistor 7 is grounded together with the emitter of the transistor 4. The N-channel MOS transistor 8 is connected in parallel to the resistor 7 and
The drain of the transistor 8 is connected to one terminal 7 a of the resistor 7, and the source is connected to the other terminal 7 b of the resistor 7. The gate of the N-channel MOS transistor 8 is configured so that the gate potential Vg can be controlled from outside the integrated circuit by a gate voltage applied from the gate voltage application terminal 51.

The reference constant current generating circuit according to the first embodiment has a resistor 7 and an N
The circuit configuration has a channel MOS transistor 8 added. In the first embodiment, the switching operation of N-channel MOS transistor 8 changes the resistance value of the series resistance circuit including resistor 2 and resistor 7 to change the current value of current output Iout.

Next, the operation will be described. The current setting unit 10 including the resistor 2, the resistor 7, and the N-channel MOS transistor 8 is regarded as one resistor, and the current setting unit 1
The resistance of 0 is referred to as a resistor R10. First, the operation of the entire circuit will be described. Next, an N-channel MOS
The case where the transistor 8 is turned on and the case where the transistor 8 is turned off will be described.

The other terminal 1b of the resistor 1 depends on the base-emitter voltage of the transistors 3 and 4.
Is determined, and a bias current is supplied to the transistors 3 and 4 by a current flowing at a potential difference from the power supply voltage Vcc of the external power supply. The potential of one terminal of the resistor R10 (terminal connected to the emitter of the transistor 3 and the base of the transistor 4) is determined by the base-emitter voltage of the transistor 4. Voltage-current conversion is performed by the resistor R10 and the transistor 3, and a constant current is obtained as a current output Iout. In this circuit, the base-emitter voltage of the transistor is substantially a known constant value, and the current value of Iout can be set by the resistance value of the resistor R10. That is, if the resistance value of the resistor R10 can be changed, the current value of the constant current output Iout can be finely adjusted or changed.

In the first embodiment, the gate voltage is applied to the gate voltage application terminal 51 instead of physically changing the connection or changing the pattern.
Turn on or off the N-channel MOS transistor 8,
The connection between the resistor 2 and the resistor 7 is electrically controlled by the current setting unit 10 forming the resistor R10, and the resistance value of the series circuit of the resistor 2 and the resistor 7 is varied to thereby output a constant current output Iou.
Adjust or change the current value of t.

Next, the current setting unit 1 forming the resistor R10
0 will be described. First, the case where the N-channel MOS transistor 8 is on will be described. By controlling the gate voltage applied from the outside to the gate voltage application terminal 51, the gate potential Vg of the N-channel MOS transistor 8 is set to a potential or more sufficient to turn on the N-channel MOS transistor 8, and the N-channel MOS transistor 8 Is turned on. At this time, the current setting unit 10
Inside, the current flows to the ground via the resistor 2 and the N-channel MOS transistor 8, and almost no current flows to the resistor 7. That is, the resistor R10 formed by the current setting unit 10 has a resistance value in which the resistor 2 and the ON resistance of the N-channel MOS transistor 8 are connected in series. If the ON resistance of the N-channel MOS transistor 8 is sufficiently smaller than the resistance 2, the current setting unit 10
Is determined only by the resistor 2.

Next, the case where the N-channel MOS transistor 8 is off will be described. By controlling the gate voltage applied to the gate voltage application terminal 51 from the outside, the potential of the gate potential Vg of the N-channel MOS transistor 8 is set to a potential or less (usually zero) sufficient to turn off the N-channel MOS transistor 8; N channel MOS
The transistor 8 is turned off. At this time, since the N-channel MOS transistor 8 is turned off inside the current setting unit 10, the resistance value of the resistor R10 formed by the current setting unit 10 is extremely high, in which the resistors 2 and 7 are connected in series. It becomes a resistance value, and the current flows from the resistor 2 to the ground via the resistor 7. That is, the resistance value of the resistor R10 formed by the current setting unit 10 is a resistance value in which the resistor 2 and the resistor 7 are connected in series.

In the above description, the N-channel MOS transistor 8 is connected in parallel to the resistor 7, and the gate potential Vg of the N-channel MOS transistor 8 is controlled by the gate voltage applied to the gate voltage application terminal 51. , The resistance value of the series circuit in which the resistance 2 and the resistance 7 are connected in series is made variable. A MOS transistor is inserted in series into a series circuit, and the conduction state of the MOS transistor is continuously controlled between the ON state and the OFF state to vary the conduction resistance. In addition to the series circuit of the resistance 2 and the resistance 7, A plurality of series circuits of resistors having different resistance values,
, And a MOS transistor is provided in series with each of the series circuits.
The gate potential of the OS transistor is controlled by gate voltages applied from different gate voltage application terminals, and each M
The OS transistor may be turned on or off to select one of the series circuits provided in parallel.

As described above, according to the first embodiment, it is possible to re-manufacture the chip itself, revise the mask, and without using the FIB or the laser cutter.
By controlling the gate potential Vg of the N-channel MOS transistor 8 to be turned on or off by the gate voltage applied to the gate voltage application terminal 51 from the outside, the resistance value of the resistor R10 formed by the current setting unit 10 is changed. This has the effect that the current value of the constant current source can be changed.

Embodiment 2 In the second embodiment, a case where the present invention is applied to a differential amplifier circuit will be described as an example. FIG. 2 is a circuit diagram showing a configuration of the differential amplifier circuit according to the second embodiment. In the figure, 11, 12, 13 and 14 are load resistors, 15 is an emitter resistor, 16 and 17 are NPN transistors constituting a differential pair, and 18 and 19 are switches P
Channel MOS transistor, 52 is a P-channel MOS
A gate voltage application terminal 53 to which a gate voltage for externally controlling the gate potential of the transistor 18 is applied;
Is a gate voltage application terminal to which a gate voltage for externally controlling the gate potential of the P-channel MOS transistor 19 is applied.

Two P-channel MOS transistors 1
Reference numerals 8 and 19 are connected in parallel to the resistors 11 and 13, respectively, and the respective gate potentials Vg can be controlled by the gate voltages applied to the gate voltage application terminals 52 and 53.

A portion composed of the resistors 11 and 12 and the P-channel MOS transistor 18 and a portion composed of the resistors 13 and 14 and the P-channel MOS transistor 19 are referred to as variable load resistors 22 and 23, respectively.

In the differential amplifier as shown in FIG. 2, the gain is determined by the ratio of the resistance values of the variable load resistance parts 22 and 23 and the resistance value of the emitter resistance 15. Therefore, the variable load resistance section 22,
The gain can be changed by changing the resistance value of the resistor 23.

By controlling the gate voltage Vg, the P-channel MOS transistors 18 and 19 are turned on, respectively.
It is turned off to change the resistance value formed by the variable load resistance units 22 and 23.

P channel MOS transistors 18 and 19
Are turned on and off, the variable load resistance units 22 and 23 behave in the same manner. Therefore, the relationship between the P-channel transistor 18 and the variable load resistance unit 22 will be described here. P
When the channel MOS transistor 18 is on, the resistor 11 is short-circuited in the variable load resistor section 22, and the resistance value formed by the variable load resistor section 22 is such that the resistor 12 and the on-resistance of the P-channel MOS transistor 18 are connected in series. Resulting in a combined resistance value. P channel MOS transistor 18
If the ON resistance of the resistor 13 is sufficiently smaller than that of the resistor 13, the variable load resistor section 22 behaves as if only the resistor 12 exists.

On the other hand, P-channel MOS transistor 18
Is off, the resistance 11 and the resistance 12 are connected in series in the variable load resistance section 22, and the variable load resistance section 2
The resistance value formed by 2 is a combined resistance value in which the resistors 11 and 12 are connected in series.

As described above, in the second embodiment, the resistance values formed by the variable load resistance portions 22 and 23 can be changed by external control, and a physical change can be applied to the chip itself. Without changing the gain of the differential amplifier.

Embodiment 3 In the third embodiment, R
An example in which the present invention is applied to a C low-pass filter will be described. FIG. 3 is a circuit diagram showing a configuration of the RC low-pass filter according to the third embodiment. In the figure, 24 is a resistor, 2
Reference numerals 5 and 26 denote capacitors, reference numeral 27 denotes an N-channel MOS transistor serving as a switch, and reference numeral 54 denotes a gate voltage application terminal to which a gate voltage for controlling the gate potential Vg of the N-channel MOS transistor 27 is applied. A portion composed of the capacitors 25 and 26 and the N-channel MOS transistor 27 is referred to as a capacitance setting section 29. N channel M
The OS transistor 27 is connected in parallel to the capacitor 26, and the gate potential Vg can be controlled by a gate voltage applied to the gate voltage application terminal 54 from outside.

By externally controlling the gate potential Vg of the N-channel MOS transistor 27 to turn on and off the N-channel MOS transistor 27, the capacitance setting unit 2
9, the capacitance value of only the capacitor 25,
The capacitance value can be changed to a value where the capacitors 25 and 26 are connected in series.

In the above description, the N-channel MOS
Although the configuration is such that the transistor 27 is connected in parallel to the capacitor 26, the components of the filter are connected in series,
It is also possible to use a MOS transistor as the switch means to combine in parallel, and to make fine adjustments and changes to the frequency characteristics including the cutoff frequency of the filter.

Also in the third embodiment, the gate potential Vg of the N-channel MOS transistor 27 is controlled by the gate voltage applied to the gate voltage application terminal 54 from outside without physically changing the chip itself. As a result, the frequency characteristics including the cutoff frequency of the low-pass filter can be finely adjusted or changed.

Embodiment 4 FIG. In each of the above embodiments, the description has been made assuming that control is performed by switching the MOS transistor. However, in each of the above embodiments, the conduction state of the MOS transistor is continuously changed between the off state and the on state. The current setting is performed by continuously changing the gate voltage applied from the gate voltage application terminal and adjusting the gate potential Vg of the MOS transistor in an analog manner so as to function as a resistance element that changes the conduction resistance. It is possible to continuously change the circuit constants of the unit 10, the variable load resistance units 22, 23, and the capacitance setting unit 29. As a result, the characteristics determined externally by the circuit constants, that is, the constant current output Iout, without physically changing the chip itself,
It is possible to continuously finely adjust or change frequency characteristics including gain and cutoff frequency.

[0032]

As described above, according to the present invention, there is provided a MOS transistor which is connected in parallel to a passive resistance element and whose gate potential is controlled from the outside and whose conduction state continuously changes between an on state and an off state. A current setting unit that varies a constant of a circuit including a passive resistance element according to a gate potential of the MOS transistor and varies a current value of the constant current generation circuit;
A gate voltage application terminal for externally applying the gate potential of the MOS transistor is provided, so that the gate voltage of the MOS transistor is externally controlled without physically changing the chip itself. This has the effect that the current value of the constant current generating circuit can be finely adjusted or changed.

According to the present invention, the MOS which is connected in parallel to the passive resistance element and which functions as a resistance element whose gate potential is controlled from the outside and whose conduction state changes continuously between the ON state and the OFF state and the conduction resistance changes. Having a transistor,
A variable load resistance section for varying the constant of a circuit including a passive resistance element according to the gate potential of the MOS transistor to vary the gain of the amplifier circuit; a gate voltage application terminal for externally applying a gate potential to the gate of the MOS transistor; Therefore, there is an effect that the gain of the amplifier circuit can be finely adjusted or changed by externally controlling the gate voltage of the MOS transistor without physically changing the chip itself.

According to the present invention, there is provided a MOS transistor which is connected in parallel to a passive capacitance element and whose gate potential is controlled from the outside and whose conduction state continuously changes between an on state and an off state. It is configured to include a capacitance setting unit that varies a constant of a circuit including a passive capacitance element by a potential and varies a frequency characteristic of a filter circuit, and a gate voltage application terminal for externally applying a gate potential of a MOS transistor. Therefore, there is an effect that the frequency characteristic of the filter circuit can be finely adjusted or changed by externally controlling the gate voltage of the MOS transistor without physically changing the chip itself.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a reference constant current generation circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a differential amplifier circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of an RC low-pass filter according to Embodiment 3 of the present invention.

FIG. 4 is a circuit diagram showing an example of a constant current circuit for explaining a conventional technique.

[Description of Signs] 1, 2, 7 Resistance (passive resistance element), 8, 27 N-channel MOS transistor, 10 Current setting unit, 18, 1
9 P-channel MOS transistor, 22, 23 Variable load resistance part, 25, 26 capacitor, 29 Capacity setting part, 51, 52, 53, 54 Gate voltage application terminal.

Claims (3)

[Claims] 1. A semiconductor integrated circuit having a passive resistance element and a constant current generating circuit whose current value is determined by a resistance value of the passive resistance element, wherein the semiconductor integrated circuit is connected in parallel to the passive resistance element and externally connected to the passive resistance element. An MO that functions as a resistance element whose gate potential is controlled and the conduction state changes continuously between the ON state and the OFF state and the conduction resistance changes
A current setting unit having an S transistor, varying a constant of a circuit including the passive resistance element by the gate potential of the MOS transistor, and varying the current value of the constant current generating circuit; A semiconductor integrated circuit comprising: a gate voltage application terminal for externally applying a gate potential. 2. A semiconductor integrated circuit having a passive resistance element and an amplifier circuit whose gain is determined by a resistance value of the passive resistance element, wherein the gate potential is externally connected to the passive resistance element in parallel. M that functions as a resistance element that is controlled and continuously changes its conduction state between an on state and an off state to change its conduction resistance
A variable load resistance section having an OS transistor, varying a constant of a circuit including the passive resistance element by the gate potential of the MOS transistor, and varying the gain of the amplifier circuit; And a gate voltage application terminal for externally applying a voltage. 3. A semiconductor integrated circuit having a passive capacitance element and a filter circuit whose frequency characteristic is determined by a capacitance value of the passive capacitance element, wherein the gate potential is externally connected to the passive capacitance element in parallel. That functions as a resistance element whose conduction state changes continuously between the ON state and the OFF state and the conduction resistance changes.
A capacitance setting unit having an OS transistor, varying a constant of a circuit including the passive capacitance element by the gate potential of the MOS transistor, and varying a frequency characteristic of the filter circuit; and applying the gate potential to the gate of the MOS transistor. A semiconductor integrated circuit comprising a gate voltage application terminal for externally applying a voltage.