JPH10190363A - Feedback amplifier circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feedback amplifier circuit capable of shortening time until a state capable of a stable and normal operation is restored from an instable state. SOLUTION: A feedback circuit 2 for feeding back a part of the output of an amplifier circuit 1 to an input side is connected to the amplifier circuit 1 and a high resistance element 3 for stabilizing the operation of the feedback circuit 2 is connected serially to the feedback circuit 2. Then, a switching circuit 4 for controlling whether or not a current is made to flow to the high resistance element 3 is connected parallelly to the high resistance element 3 and a control circuit 5 for controlling the operation of the switching circuit 4 is connected to the switching circuit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a feedback amplifier circuit including a high resistance element.

[0002]

2. Description of the Related Art FIG. 11 shows a conventional feedback amplifier circuit including a high resistance element. Reference numeral 1 denotes an amplifier circuit. A feedback circuit 2 feeds back a part of the output of the amplifier circuit 1 to the input side. That is, the input terminal portion of the amplifier circuit 1 is connected to the feedback circuit 2
Will be charged through. Reference numeral 3 denotes a high-resistance element, which is connected in series with the feedback circuit 1 and stabilizes the operation of the feedback circuit 1.

In the above circuit configuration, especially when the input signal is very small, it is necessary to reduce the noise generated inside the circuit. However, since the noise generated by the high resistance element 3 is inversely proportional to the resistance value, a low noise circuit is required. In order to realize this, the resistance value must be made considerably high.

FIG. 12 is a schematic basic circuit diagram of the above figure.
The amplifier circuit 1 includes an operational amplifier OP1, a feedback capacitor Cf, and a reference potential Vr, and the feedback circuit 2 includes an operational amplifier O1.
P2, a capacitor C1, a reference potential Vr, and a resistor R1.

[0005] A part of the output of the operational amplifier OP1 is input to the positive terminal of the operational amplifier OP2, and the output of the operational amplifier OP2 is input to the negative terminal of the operational amplifier OP1 via the high resistance element Ri. The positive terminal of the operational amplifier OP1 has the reference potential Vr
, And the negative terminal of the operational amplifier OP2 is connected to ground via the resistor R1 and the reference potential Vr, and the negative terminal of the operational amplifier OP2 and the output side are connected to the capacitor C1.
Connected through.

The input terminal and the ground are connected to a capacitor Cs
Are connected via the pyroelectric element 6.

This circuit functions as a current-voltage conversion circuit for converting an input current signal from the pyroelectric element 6 into an output voltage. At this time, the conversion impedance Z (s) is

[0008]

(Equation 1)

## EQU1 ## here,

[0010]

(Equation 2)

[0011] In other words, the above equation is

[0012]

(Equation 3)

Rewritten as follows. As described above, the conversion impedance of the current-voltage conversion circuit has the frequency characteristic of the band-pass filter. Where ω0
Is the center frequency, and Q is what is commonly called selectivity.

Further, since the input signal from the pyroelectric element 6 is very small, this circuit is required to have low noise. However, as one of the dominant noise components in this circuit, a resistor Ri (high) is used. There is thermal noise due to the resistance element 3), and in order to suppress this, the resistance value of Ri is a high resistance of about 1T (tera) Ω or more.

Next, an operation when power is supplied to the feedback amplifier circuit will be described with reference to FIG. When the power is supplied to the feedback amplifier circuit, the input terminal receives the reference voltage V.
Although trying to be equal to r, the pyroelectric element 6 is equivalently a capacitance, and its output impedance is very high.

Therefore, the path for charging the input terminal is only the path from the high resistance element 3 via the feedback circuit 2. However, since the high-resistance element 3 also has a high resistance for the above-described reason, a long time is required for charging.

[0017]

In the feedback amplifier circuit having the above configuration, if a high-resistance element 3 having a high resistance value is used in order to realize a low-noise circuit, the charging speed of the input terminal portion is reduced. For this reason, there is a problem that a considerably long time is required from a state in which the circuit is not stable, such as when the power is turned on, to a stable state in which the circuit can operate normally.

The present invention has been made in view of the above points, and an object of the present invention is to reduce the time required to return from an unstable state to a stable and normal operation state. An object of the present invention is to provide a feedback amplifier circuit which can be used.

[0019]

According to the first aspect of the present invention,
In a feedback amplifier circuit including an amplifier circuit, a feedback circuit for feeding back part of the output of the amplifier circuit to the input side, and a high-resistance element connected in series with the feedback circuit to stabilize the operation of the feedback circuit. A switch circuit that is connected in parallel with the high-resistance element and controls whether or not a current flows through the high-resistance element, and a control circuit that controls the operation of the switch circuit. Things.

According to a second aspect of the present invention, in the feedback amplifier circuit of the first aspect, a buffer resistor is added in series with the switch circuit.

According to a third aspect of the present invention, in the feedback amplifier circuit according to the first or second aspect, the control circuit comprises a series circuit of a capacitor and a charging resistor for charging the capacitor. A circuit is connected between a power supply and a ground, and the switch circuit is controlled based on a potential at a connection point between the charging resistance element and the capacitor.

According to a fourth aspect of the present invention, in the feedback amplifying circuit according to the third aspect, an element having the same characteristic as the high resistance element is used as the charging resistance element.

According to a fifth aspect of the present invention, in the feedback amplifier circuit according to the third or fourth aspect, a buffer circuit is added to the control circuit, and the connection point and the switch circuit are connected via the buffer circuit. It is characterized in that it is connected.

According to a sixth aspect of the present invention, in the feedback amplifier circuit of the fifth aspect, the buffer circuit is configured by connecting a first inverter and a second inverter in series, and the first inverter Is increased, and the threshold value of the second inverter is decreased.

According to a seventh aspect of the present invention, in the feedback amplifying circuit according to the fifth or sixth aspect, the buffer circuit is constituted by connecting a first inverter and a second inverter in series. The first inverter has a hysteresis characteristic.

According to an eighth aspect of the present invention, in the feedback amplifier circuit according to any one of the fifth to seventh aspects, a plurality of sets of the high resistance element and the switch circuit are connected in series with the feedback circuit, and A different number of the buffer circuits are interposed between the circuit and the connection point.

According to a ninth aspect of the present invention, in the feedback amplifier circuit of the first or second aspect, the control circuit is constituted by a programmable digital circuit.

According to a tenth aspect of the present invention, in the feedback amplifying circuit according to the ninth aspect, a plurality of sets of the high-resistance element and the switch circuit are connected in series with the feedback circuit, and each of the switch circuits is connected. It is characterized by being controlled by the digital circuit.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic configuration diagram showing a feedback amplifier circuit according to an embodiment of the present invention. Reference numeral 1 denotes an amplifier circuit. A feedback circuit 2 feeds back a part of the output of the amplifier circuit 1 to the input side. Reference numeral 3 denotes a high resistance element which is connected in series with the feedback circuit 2 and stabilizes the operation of the feedback circuit 2. A switch circuit 4 is connected in parallel with the high resistance element 3 and controls whether or not a current flows through the high resistance element 3. In other words, control is performed such that current does not flow through the high resistance element 3 when the switch circuit 4 is on, and current flows through the high resistance element 3 when the switch circuit 4 is off. Reference numeral 5 denotes a control circuit for performing on / off control of the switch circuit 4.

FIG. 2 is a schematic basic circuit diagram of the above figure. The amplifier circuit 1 includes an operational amplifier OP1, a feedback capacitor Cf, and a reference potential Vr. The feedback circuit 2 includes an operational amplifier OP1.
2, a capacitor C1, a reference potential Vr and a resistor R1.

Part of the output of the operational amplifier OP1 is input to the positive terminal of the operational amplifier OP2, and the output of the operational amplifier OP2 is input to the negative terminal of the operational amplifier OP1 via the high resistance element 3. The positive terminal of the operational amplifier OP1 is connected to ground via the reference potential Vr, the negative terminal of the operational amplifier OP2 is connected to ground via the resistor R1 and the reference potential Vr, and the negative terminal of the operational amplifier OP2 and the output side have a capacitance C1. Connected through.

The input terminal and the ground are connected to a capacitance Cs
Are connected via the pyroelectric element 6.

Next, the operation of this embodiment will be described. When the circuit operation is unstable, such as when the power of the feedback amplifier circuit is turned on or when noise is applied to the circuit, the control circuit 5 turns on the switch circuit 4 to switch the current flowing through the high resistance element 3 The circuit 4 is bypassed. Since the switch circuit 4 has a smaller resistance value than the high resistance element 3,
When the time required for the circuit to reach a stable state is short, and when the circuit comes to a stable state and operates normally, the control circuit 5 turns off the switch circuit 4 so that the current is conducted to the high resistance element 3. . Thereafter, after a transition period, the circuit enters a state where stable operation is possible.

Therefore, in the present embodiment, the current flowing through the high resistance element 3, which causes the time required for the feedback amplifier circuit to perform stable and normal operation, is increased until the operation of the circuit is stabilized. Since the bypass is performed by the switch circuit 4 whose resistance value is much smaller than that of the resistance element 3, the time required for the circuit operation to change from an unstable state to a stable and normal operation state, such as when power is turned on, is reduced. Can be shortened.

Embodiment 2 = FIG. 3 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention. In the present embodiment, in addition to the feedback amplifier circuit shown in FIG. 1, a buffer resistance element 7 is connected in series with the switch circuit 4, so that even when no current flows through the high resistance element 3, A current flows through the buffering resistance element 7.

Therefore, in the present embodiment, since the resistance is always present in the circuit regardless of the ON / OFF state of the switch circuit 4, the circuit becomes unstable when the high-resistance element 3 is completely short-circuited. And oscillation can be prevented.

Embodiment 3 = FIG. 4 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention. In the present embodiment, the control circuit 5 of the feedback amplifier circuit shown in FIG.
Is connected in series with a charging resistor 9 used to charge the battery. A power supply is connected to the charging resistor 9 on a side different from the connection point 10,
Is connected to the ground, and the connection point 10 between the capacitor 8 and the charging resistor 9 is connected to the switch circuit 4. The potential of the connection point 10, that is, the capacitor 8 ON / OFF of the switch circuit 4 is controlled by the charging potential of the switch circuit 4.

Next, an operation when power is supplied to the feedback amplifier circuit of the present embodiment will be described. Capacitor 8
Is not charged, the switch circuit 4 is on, and the current flowing through the high resistance element 3 is bypassed by the switch circuit 4. When power is supplied to the feedback amplifier circuit, the capacitor 8 is charged via the charging resistor 9, and the potential of the connection point 10 is higher than the rise of the power supply by the time constant of the capacitor 8 and the charging resistor 9. And get up slowly. That is, the higher the capacitance of the capacitor 8 and the resistance value of the charging resistor 9, the longer the rise time. Since the switch circuit 4 is turned on until the potential of the connection point 10 reaches a certain threshold, the feedback amplifier circuit rapidly approaches a stable state.

When the potential at the connection point 10 reaches the threshold value,
The switch circuit 4 is turned off, the current is conducted to the high resistance element 3, and the feedback amplifier circuit settles in a state where it can operate normally after a transition period.

If a discharge circuit (not shown) for discharging the capacitor 8 is provided, when the operation of the feedback amplifier circuit becomes unstable due to noise or the like, the switch circuit 4 is turned on again by the discharge circuit. However, the time until the operation of the feedback amplifier circuit is stabilized can be reduced by the same operation as described above.

If elements having the same temperature characteristics or the like are used as the high resistance element 3 and the charging resistance element 9, for example, each of the high resistance element 3 and the charging resistance element 9 depends on the temperature characteristics and the like. The variation in resistance value is the same. Therefore, when the resistance value of the high resistance element 3 increases due to fluctuation, when the switch circuit 4 is turned off, the high resistance element 3
However, it takes extra time to reach a stable state due to the increase in the resistance value of the charging resistance element 9, but the resistance value of the charging resistance element 9 also increases similarly to the high resistance element 3. As a result, the charging time of the capacitor 8 becomes longer, so that the time during which the switch circuit 4 is on becomes longer, and as a result, the time until the stable operation becomes possible due to fluctuations in the resistance value of the high resistance element 3 becomes longer. Can be prevented.

Embodiment 4 = FIG. 5 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention. In the present embodiment, in the feedback amplifier circuit shown in FIG.
A connection point 10 with the switch circuit 4 and a buffer circuit 11
It is configured to be connected via a. Buffer circuit 11
Is constituted by an inverter or the like, and generates a slight delay time from when a signal is input to when it is output.

Therefore, in the present embodiment, the time from when the signal is input to the buffer circuit 11 to when the signal is output to the buffer circuit 11 is used to delay the time until the switch circuit 4 that is on is turned off. it can. In other words, in order to extend the time during which the switch circuit 4 is turned on, the time during which the switch circuit 4 is turned on by the buffer circuit 11 can be reduced without increasing the capacitance of the capacitor 8 which directly affects the circuit size of the feedback amplifier circuit. Can be longer.

Embodiment 5 = FIG. 6 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention. In the present embodiment, in the feedback amplifier circuit shown in FIG.
1a and 11b are connected in series so that the threshold value of the inverter 11a is high and the threshold value of the inverter 11b is low.

Next, the operation of this embodiment will be described. As in the third embodiment, the switch circuit 4 is switched from on to off by the potential of the connection point 10. At this time, if the inverter 11a is set higher than the threshold value of the normal inverter, the time from when a signal is input to when the signal is output can be lengthened. As a result, the time during which the switch circuit 4 is on is reduced. Can be longer. Also,
Similarly, by making the threshold value of the inverter 11b at the next stage lower than the threshold value of the normal inverter, the time from when a signal is input to the inverter 11b to when the signal is output can be lengthened. 4 can be made longer.

Note that either one of the inverters 11a,
As described above, the delay time of the signal in the impeller can be extended simply by setting the threshold value for 11b.

Therefore, in the present embodiment, the buffer circuit 11 is connected to the buffer circuit 11 without increasing the capacitance of the capacitor 8 which directly affects the circuit size of the feedback amplifier circuit in order to lengthen the ON time of the switch circuit 4. By setting the threshold values of the configured impellers 11a and 11b, the time during which the switch circuit is on can be extended.

Embodiment 6 = FIG. 7 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention. In the present embodiment, in the feedback amplifier circuit shown in FIG.
1c and 11d are connected in series, so that the inverter 11c has a hysteresis characteristic.

Next, the operation of this embodiment will be described. As in the third embodiment, the switch circuit 4 is switched from on to off by the potential of the connection point 10. At this time, since the inverter 11c has a hysteresis characteristic, it works so as to absorb the noise generated in the capacitor 8, the charging resistance element 9 and the like, and to reduce the influence of the noise on the switch circuit 4. The inverter 11d inverts the polarity of the signal inverted by the inverter 11c again to return to the original state.

Therefore, in this embodiment, since the inverter 11c having the hysteresis characteristic works so as to absorb the noise included in the signal to the switch circuit 4, the inverter 11c from the capacitor 8, the charging resistor 9 and the like to the switch circuit 4 The effect of transmitted noise can be reduced.

Embodiment 7 = FIG. 8 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention. In the present embodiment, a feedback circuit 2 that feeds back a part of the output of the amplifier circuit 1 to the input side is connected to the amplifier circuit 1, and a parallel circuit of a high resistance element 3a and a switch circuit 4a, a high resistance element 3b, and a switch A series circuit with a parallel circuit with the circuit 4b is connected in series to the feedback circuit 2. The connection point 10 between the capacitor 8 and the charging resistance element 9 and the switch circuit 4a are connected via inverters 11c and 11d, and the connection point 10 and the switch circuit 4b are connected via a series circuit of inverters 11c to 11f. ing.

Incidentally, three or more sets of parallel circuits of high resistance elements and switch circuits may be connected in series with the feedback circuit 2.

Next, the operation of this embodiment will be described. The on / off control of the switch circuit 4 is the same as in the sixth embodiment. However, the switch circuit 4a and the switch circuit 4b differ in the number of inverters between the connection point 10 and the switch circuit b in the circuit configuration shown in FIG. Therefore, after the high resistance element 3a becomes conductive, the high resistance element 3b becomes conductive.

Therefore, in this embodiment, the connection point 1
By adding an arbitrary number of inverters between 0 and each of the switch circuits 4a and 4b,
4b can be set arbitrarily until the high-resistance element 3a,
The resistance value of the high-resistance elements 3a and 3b can be gradually increased through several stages instead of switching from the bypass state to the conduction state from the bypass state. Noise and unstable operation of the circuit can be prevented.

Embodiment 8 = FIG. 9 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention. In the present embodiment, in the feedback amplifier circuit shown in FIG. 1, the control circuit 5 is configured by a programmable digital circuit 12 having a counter function and the like.

Therefore, in this embodiment, the time during which the switch circuit 4 is on can be freely set by changing the program of the digital circuit 12.

Embodiment 9 = FIG. 10 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention. In the present embodiment, the amplification circuit 1
Is connected to a feedback circuit 2 for feeding back a part of the output of the amplifier circuit 1 to the input side, and a parallel circuit of a high resistance element 3a and a switch circuit 4a, a high resistance element 3b and a switch circuit 4
A series circuit with a parallel circuit with b is connected to the feedback circuit 2 in series. A digital circuit 12 is connected to the switch circuits 4a and 4b.

It should be noted that three or more parallel circuits of the high resistance element and the switch circuit may be connected in series with the feedback circuit 2.

Therefore, in the present embodiment, the time until the plurality of switch circuits 4a and 4b are turned off can be freely set by the digital circuit 12. Further, since the resistance values of the high resistance elements 3a and 3b of the feedback amplifier circuit can be easily controlled by turning on / off the switch circuits 4a and 4b, the resistance value of the feedback amplifier circuit can be set freely according to the application. .

[0061]

According to the first aspect of the present invention, the amplifier circuit, a feedback circuit for feeding back a part of the output of the amplifier circuit to the input side, and a series connection with the feedback circuit to stabilize the operation of the feedback circuit. In a feedback amplifier circuit including a high-resistance element, a switch circuit that is connected in parallel with the high-resistance element and controls whether a current flows through the high-resistance element and a control circuit that controls the operation of the switch circuit are added. Because it was
It is possible to provide a feedback amplifier circuit that shortens the time required for the circuit operation to change from an unstable state at power-on or the like to a stable and normal operation state.

According to a second aspect of the present invention, in the feedback amplifying circuit according to the first aspect, a buffer resistance element is added in series with the switch circuit. It is possible to prevent unstable operation and easy oscillation.

According to a third aspect of the present invention, in the feedback amplifier circuit according to the first or second aspect, the control circuit comprises a series circuit of a capacitor and a charging resistor for charging the capacitor, and the series circuit is connected to a power supply. And the ground, and controls the switch circuit based on the potential of the connection point between the charging resistor and the capacitor. Since the high-resistance element becomes conductive at the point where the voltage is exceeded, the time required for the feedback amplifier circuit to return from an unstable state such as when power is turned on to a stable and normal operation state can be reduced.

According to a fourth aspect of the present invention, in the feedback amplifying circuit according to the third aspect, an element having the same characteristics as the high resistance element is used as the charging resistance element. Variations in the resistance values become the same due to temperature characteristics and the like, and it is possible to prevent the time required for the feedback amplifier circuit to operate stably due to the fluctuations in the resistance values to be extended.

According to a fifth aspect of the present invention, in the feedback amplifier circuit of the third or fourth aspect, a buffer circuit is added to the control circuit, and the connection point and the switch circuit are connected via a buffer circuit. Therefore, the time required for the signal for turning off the switch circuit to propagate through the buffer circuit can be delayed, and the time required for the high-resistance element to become conductive can be delayed.

According to a sixth aspect of the present invention, in the feedback amplifier circuit of the fifth aspect, the buffer circuit is configured by connecting the first inverter and the second inverter in series, and the threshold value of the first inverter is determined. And the threshold of the second inverter is lowered, so that the time from when a signal is input to when it is output in the first and second inverters can be delayed by setting the threshold. In addition, it is possible to delay a time until the high resistance element is conducted.

According to a seventh aspect of the present invention, in the feedback amplifying circuit according to the fifth or sixth aspect, the buffer circuit is constituted by connecting a first inverter and a second inverter in series. Is made to have a hysteresis characteristic, so that when noise occurs in the control circuit, the influence of the noise transmitted from the control circuit to the switch circuit can be reduced.

According to an eighth aspect of the present invention, in the feedback amplifying circuit according to the fifth to seventh aspects, a plurality of sets of a high resistance element and a switch circuit are connected in series with the feedback circuit, and the switch circuit and the connection point are connected. And a different number of buffer circuits between them, so that the feedback amplifier circuit does not suddenly switch from the state where the high resistance element is bypassed to the state where it is conductive, but the resistance value of the high resistance element. Gradually increases after several stages, and it is possible to prevent noise generated by sudden switching and unstable operation of the circuit.

According to a ninth aspect of the present invention, in the feedback amplifying circuit according to the first or second aspect, the control circuit is constituted by a programmable digital circuit. The time from bypassing the current flowing through to the high resistance element can be set freely.

According to a tenth aspect of the present invention, in the feedback amplifying circuit of the ninth aspect, a plurality of sets of a high resistance element and a switch circuit are connected in series with the feedback circuit, and each switch circuit is controlled by a digital circuit. I decided to
The operation time of the plurality of switch circuits can be freely set, and a resistance element having a desired resistance value can be selected from the plurality of high resistance elements.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a feedback amplifier circuit according to an embodiment of the present invention.

FIG. 2 is a schematic basic circuit diagram of the upper diagram.

FIG. 3 is a schematic configuration diagram illustrating a feedback amplifier circuit according to another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram illustrating a feedback amplifier circuit according to another embodiment of the present invention.

FIG. 5 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention.

FIG. 7 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention.

FIG. 9 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention.

FIG. 10 is a schematic configuration diagram showing a feedback amplifier circuit according to another embodiment of the present invention.

FIG. 11 is a schematic configuration diagram showing a feedback amplifier circuit according to a conventional example.

FIG. 12 is a schematic basic circuit diagram of the upper diagram.

[Explanation of symbols]

 OP1, OP2 operational amplifier Cf feedback capacitance C1 capacitance Ri, R1 resistance Vr reference potential 1 amplification circuit 2 feedback circuit 3, 3a, 3b high resistance element 4, 4a, 4b switch circuit 5 control circuit 6 pyroelectric element 7 buffer resistance element 8 Capacitor 9 Charging resistance element 10 Connection point 11 Buffer circuit 11a to 11f Inverter 12 Digital circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshio Fujimura 1048 Kazuma Kadoma, Kadoma City, Osaka Inside Matsushita Electric Works, Ltd.

Claims (10)

[Claims] An amplifier circuit, a feedback circuit for feeding back a part of an output of the amplifier circuit to an input side, and a high resistance element connected in series with the feedback circuit for stabilizing the operation of the feedback circuit. In the feedback amplifier circuit, a switch circuit connected in parallel with the high-resistance element to control whether a current flows through the high-resistance element and a control circuit to control the operation of the switch circuit are added. A feedback amplifier circuit characterized in that: 2. The feedback amplifier circuit according to claim 1, wherein a buffer resistance element is added in series with said switch circuit. 3. The control circuit comprises a series circuit of a capacitor and a charging resistance element for charging the capacitor, wherein the series circuit is connected between a power supply and a ground, and wherein the charging resistance element and the capacitor are connected. 3. The feedback amplifier circuit according to claim 1, wherein the switch circuit is controlled based on a potential at a connection point with the feedback amplifier. 4. The feedback amplifier circuit according to claim 3, wherein an element having the same characteristics as said high resistance element is used as said charging resistance element. 5. A buffer circuit is added to the control circuit,
5. The feedback amplifier circuit according to claim 3, wherein the connection point and the switch circuit are connected via the buffer circuit. 6. The buffer circuit is configured by connecting a first inverter and a second inverter in series, and increases the threshold value of the first inverter and lowers the threshold value of the second inverter. 6. The feedback amplifier circuit according to claim 5, wherein 7. The buffer circuit according to claim 1, wherein a first inverter and a second inverter are connected in series, and the first inverter is provided with a hysteresis characteristic. 5 or Claim 6
Feedback amplifier circuit as described. 8. A plurality of sets of the high resistance element and the switch circuit are connected in series with the feedback circuit, and different numbers of the buffer circuits are interposed between the switch circuit and the connection points. 8. The feedback amplifier circuit according to claim 5, wherein: 9. The feedback amplifier circuit according to claim 1, wherein said control circuit comprises a programmable digital circuit. 10. A plurality of sets of said high-resistance element and said switch circuit are connected in series with said feedback circuit, and each of said switch circuits is controlled by said digital circuit. 9. The feedback amplifier according to 9.