JPS6238014A - Amplifier circuit with automatic range - Google Patents

Abstract

PURPOSE:To eliminate mulfunction at range switching by charging a capacitor deciding a time constant by a voltage between output voltages of an amplifier before and after amplification factor changeover in advance so as to prevent the temporary reduction of the output voltage of the amplifier caused at range changeover. CONSTITUTION:When the range is switched, since a capacitor C2 is charged by a voltage V of a capacitor charging power supply 7 before switching, an output Vout of the amplifier 3 is not lowered than the voltage (VH>=V>=VL). That is, a temporary reduction in the output voltage Vout is not caused at range switching and the range switching with fidelity to an input signal is attained without causing chattering.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an auto-ranging amplifier circuit that changes the amplification degree according to the input signal level and obtains an output signal.

Conventional technology In recent years, direct current amplifier circuits (hereinafter referred to as
The detection range of amplifier circuits (simply referred to as amplifier circuits) has been expanded, and input signals are often amplified over a range that exceeds the dynamic range of the amplifier circuit itself. For this reason,
A method is adopted in which an input signal is amplified and an output signal is obtained by switching the amplification degree of the amplifier circuit.

A conventional auto-range amplifier circuit will be explained below.

Fig. 3 shows the configuration of a conventional two-stage amplification switching type auto-ranging amplifier circuit.
This is an example using an inverting amplifier circuit using the amplification degree switching means 8b, and the amplification degree is changed by switching the feedback resistors R1 and R2. Capacitors C1 and 02 are connected in parallel to the feedback resistors R4 and R2, respectively, to provide a time constant for the degree of amplification and to stabilize the amplification operation.

The range setting section 9 is composed of two comparators 9c and 9d for range switching, reference power supplies 9a and 9b, an inverter 9q, and a range holding section 9f (FIG. 3 shows an example using a flip-flop 9f1). Ru.

Figure 4 shows the conventional auto-range amplifier circuit configured as described above. The operation when a signal waveform as shown in FIG. 4 is input will be explained based on the waveforms of each part shown in FIG. Note that the feedback resistance R1 of the OP amplifier 1a in FIG.
and R2 are set as R,=10XR2. Further, the range switching section 9 has a reference voltage vI+ for switching from the low signal input range to the high signal input range, and a reference voltage vL for switching from the high signal input range to the low signal input range. The reference voltage v8·V is set to vL''':
o, o s x vH is often set.

Input signal V engineering. When is zero, the output of OP amplifier 8B becomes zero. At this time, the comparator 9d (
The output (for switching from a low amplification range to a high amplification lens) is inverted by an inverter 9q, and a Philips 70 tube 9f is inverted.
1 is reset and the output q is set to "L". The output of the flip-flop 9f1 is applied to the switching means 8b in the amplification degree switching type amplifier circuit 8, and operates the switch 8b1 via the driver 8b2. By this operation, the feedback loop of the OP amplifier 8a is connected to the resistor R1 and the capacitor C1 through the contact of the switch 8b1, and this state is maintained.

Next, input signal V engineering. When gradually increases, the op amp 8
The output of O is Vou, knee R, / R engineering x v engineering. The output determined by is obtained. Here V. When ut reaches the switching voltage vL from the low amplification range to the high amplification range as shown in FIG.
The output is inverted and applied to the reset input of the flip-flop 9f1. However, this only releases the reset input of the flip-flop 9f1, and the output does not change as shown in FIG. 4e. Furthermore, the input signal vi
n increases, and the output V of the OP amplifier 8a. When ut reaches the switching voltage vH from the high amplification range to the low amplification range, the output of the comparator 9c is inverted and [waveform al is added to the set input of the phillip flop 9f1, and the output of the philip flop 9f1 is Invert [waveform e],
The output of the Philips flop 9f1 is applied to the driver 8b2 in the amplification degree switching type amplifier circuit 8 to operate the switch 8b1 and serve as the feedback resistor R2 of the op-amp 8a. At the same time, capacitor C2 is connected in a feedback loose manner. As a result, the output of the amplification degree switching type amplifier circuit 8 is 1
/10 and is applied to the range setting section.

Problems to be Solved by the Invention However, such a system has the following problems. The range changes and the OP amplifier 8a feed
When the dopuck resistance becomes R2, the capacitor C2 connected to the switched range is initially empty, so the capacitor C2 is charged at the time of switching, and the comparator 9d is activated [see Figure 4]. The waveform is shown in FIG. 4V. This results in a temporary voltage drop as shown in ut. This decrease inverts the output of the flip-flop 9f1 and applies it again to the switching means 8b, switching the feedback resistance of the OP amplifier from R2 to R1 [Fig. 4 VOut,
Waveforms are shown in a, b, and c. ],, When the feedback resistance of the OP amplifier Sa becomes R1, the OP amplifier 8
The output of a is 10 times greater. Capacitor C4 is connected to resistor R4.
are connected in parallel, and capacitor C1 is already charged with charge during operation in the high amplification range.
The output of the OP amplifier 8a exceeds the reference voltage vI(, and the range setting section 9 operates to set the feedback resistance of the OP amplifier 8a to R2 again [Fig. 4 V.uta, b).
The waveform is shown at +8. ]. By repeating such operations, the amplification degree is frequently switched until the terminal voltage of the capacitor C2 of the low amplification degree sensor becomes equal to or higher than the reference voltage vL.

In this way, the output V of the amplification degree switching type amplifier circuit 8. As shown in FIG. 4, ut fluctuates within the period indicated by 1 and has a waveform different from that of the input signal.

Means for Solving the Problems The means of the present invention for solving the above problems is to connect a plurality of capacitors in parallel to determine a time constant, and to switch the amplification level +'+
A power supply that charges the capacitor with a voltage between the output voltages of the amplifiers after rj and a capacitor connection switching section that operates based on a signal from the range setting section and switches the connection of the capacitor are provided.

action The effect of this means is as follows.

By charging the capacitor that determines the time constant in advance with a voltage between the output voltages of the amplifier before and after switching the amplification level, a temporary drop in the output voltage of the amplifier that occurs when switching ranges can be prevented, and malfunctions when switching ranges can be prevented. Eliminate.

EXAMPLE An example of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment in which the degree of amplification is switched to two stages: 1x and 10x. In FIG. 1, 1 is an amplification switching section, 2 is a range setting section, 3 is an amplifier, 4 is a capacitor connection switching section 5 is a capacitor that determines a time constant, and 6 is a power supply for charging the capacitor.

The amplification switching unit 1 includes a driver 1a for switching the switch 1d.
, feedback resistors 1b and 1C, and a switch 1d for switching feed bank resistors 1b and 1C.

The range setting section 2 is a reference power source 2a for range switching.

2b, comparators 2C and 2d, and range holding part 2f
(In the case of the second embodiment, a flip-flop is used) and an inverter 2q.

In this embodiment, the resistance values of the feedback resistors 1b and 1c are set to R, :10XR2, and the range switching reference voltage 2a
, 2b, 2a has a voltage vL for switching from a high signal input range to a low signal input range, and 2b has a voltage vll for switching from a low signal input range to a high signal input range.

Also, v)1. ! :vL is set to have the relationship vH>10vL. Furthermore, the power supply 6 for capacitor charging
The voltage value V is set to have a relationship of V, ≧V≧vL.

The capacitor connection switching unit 4 includes a driver 4a and switches 4b and 4C for switching capacitor connections.

The operation of the auto-range amplifier circuit of this embodiment configured as described above will be explained below.

Input signal V engineering. When is zero, the output of amplifier 3 is zero.

At this time, the output of the comparator 2d (for switching from the low amplification range to the high amplification range) in the range setting section 2 is inverted by the inverter 2q, which resets the flip-flop 2r and sets the output Q to "L". do. The output of the Irisobufrosop 2f is applied to the driver 1a in the amplification switching unit 1 and the driver 4a in the capacitor connection switching unit 4, and operates the feedback resistance switching switch 1d and the capacitor connection switching switches 4b and 40. let Due to this operation, the feedback loop of amplifier 3 has 1d and 4
b, 4C connects resistor R1 and capacitor C1,
One of the terminals of the capacitor C2 is grounded, and the other terminal is connected to the power supply 6 (() for charging the capacitor, and is charged with a voltage V.

Next, input signal V engineering. When V gradually increases, the output of the amplifier 3 is determined by vout = -R+ / "o x vin. Here, when vOut reaches the switching voltage vL from the low signal input range to the high signal input range, When this happens, the output of the comparator 2d in the range setting section 2 is inverted and the reset input of the Philips 70 knob 2f is released, but the output Q does not change.

Furthermore, input signal V engineering. increases, and the output vo of amplifier 3
When ut reaches the switching voltage vH from the high signal input range to the low signal input range, the output of the comparator 2C is inverted and added to the cent input of the flip-flop 2f', and the output Q of the flip-flop 2f is Invert. The output of the phillip flop 2r is the driver 12L in the amplification switching section 1 and the driver 4a in the capacitor connection switching section 4.
is applied to the switch 1d for switching the feed bank resistance.
Then, the switches 4b and 40 for switching the capacitor connection are operated. As a result of this operation, the feedback loop of the amplifier 3 is connected to the resistor R2 and the capacitor C2 by the switches 1d, 4b, and 4C, and one terminal of the capacitor C1 is grounded, and the other terminal is connected to the power supply 6 for charging the capacitor. Charge with voltage V. As a result, the output of amplifier 3 is 1
/10 and is applied to the range setting section 2. When the range is switched in this way, the capacitor C2 is charged with the voltage V by the capacitor charging power supply before switching, so the output of the amplifier 3 is V. ut is the voltage V (Vl,
≧V≧vL). That is, the temporary output voltage V at the time of range switching. To perform a range switching operation faithful to an input signal without lowering ut or causing chattering.

Figure 2 shows that without providing an external power supply for charging the capacitor,
This is another embodiment of the present invention in which the reference power source 2a for range switching in the range setting section 2 is used as a power source for charging a capacitor. The operation is similar to that of the previous embodiment, and the same effects can be obtained.

Furthermore, the same effect can be obtained by using the power supply for capacitor charging and the reference power supply 2b for range switching.

If the reference power supply 2a (voltage vL) is used as the power supply for capacitor charging, the response will be good when switching to the low amplification range, while if the reference power supply 2b (voltage v11) is used as the power supply for capacitor charging, the response will be good when switching to the low amplification range. Good response when switching to range.

Effects of the Invention The auto-ranging amplifier circuit of the present invention includes an amplifier, an amplification switching unit that switches the amplification level using a plurality of resistors and is connected between the input and output of the amplifier, and a time constant that is connected in parallel to the amplification switching unit. Multiple capacitors are connected in parallel to the capacitor,
A power source that charges the capacitor with a voltage between the output voltages of the amplifier before and after switching the amplification level, a switch that operates based on a signal from the range setting section to change the connection of the capacitor, and a switch that is connected to the amplifier and adjusts the amplification level according to the input signal level. By setting the range setting section and outputting the signals for amplification switching and capacitor switching, it is possible to prevent range setting malfunctions when switching the amplification level and automatically set the amplification level according to the input signal level. Its practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an auto-ranging amplifier circuit according to an embodiment of the present invention, FIG. 2 is a block diagram of another embodiment of the present invention, and FIG.
The figure is a configuration diagram of a conventional auto-ranging amplifier circuit.
The figure shows waveforms at various parts in the conventional example shown in FIG. 1... Amplification switching unit, 2... Range setting unit, 3... Amplifier, 4... Capacitor connection switching unit, 6...・Capacitor, 6...
・・Power source, 2N・2b・・・・Reference as source, 2c・2
d...Comparator, 2f...Range holding section, 2q...Inverter. Name of agent: Patent attorney Toshio Nakao and 1 other law attorney
ゝ> Figure 4

Claims (2)

[Claims] (1) An amplifier that amplifies an input signal, an amplification switching unit that switches the amplification level using multiple resistors and is connected between the input and output of the amplifier, and a plurality of capacitors that are connected in parallel to the amplification switching unit and determine a time constant. a power supply connected in parallel to the capacitor and charging the capacitor with a voltage between the output voltages of the amplifier before and after switching the amplification level; a capacitor connection switching unit operated by a signal from the range setting unit to switch the connection of the capacitor; An auto-range amplifier circuit that is connected to an amplifier and includes a range setting section that sets the amplification degree according to the input signal level and outputs signals for switching the amplification degree and switching the capacitor. (2) The range setting section consists of two reference power supplies for range switching, two comparators that compare the reference power supplies and the amplifier output, and a range holding section that sets and maintains the amplification range using the output of the comparator. 2. The auto-range amplifier circuit according to claim 1, wherein the reference power source is a power source for charging the capacitor.