Voltage follower circuit and voltage follower

Abstract

The utility model provides a voltage follower circuit and a voltage follower. The voltage following circuit comprises an operational amplifier module, a first voltage dividing module, a second voltage dividing module, an isolation module, a feedback module, a first power supply, a second power supply and a third power supply. The first power supply and the third power supply are common-grounded, and the first power supply and the second power supply are not common-grounded; the operational amplifier module is used for outputting a first current signal when receiving the input voltage of the first power supply; the feedback module is used for outputting a feedback voltage to enable the operational amplifier module to enter a virtual short state when the first current signal is received and the third power supply supplies power, so that the feedback voltage is equal to the input voltage; the isolation module is used for outputting a target voltage when the first current signal is received and the second power supply supplies power; wherein the resistance value of the first voltage dividing module and the resistance value of the second voltage dividing module are configured to be equal, so that the target voltage is equal to the feedback voltage, namely, the target voltage is equal to the input voltage. According to the invention, the stability and the anti-interference capability during voltage following are improved.

Description

Technical Field

[0001] The present application belongs to the field of power electronics technology, and specifically relates to a voltage follower circuit and a voltage follower. Background Art

[0002] Currently, there are two common design schemes for isolated sampling circuits: one is to use an isolated operational amplifier chip or a linear optocoupler for sampling, and the other is to use a high-resistance (at least six 1MΩ in series) operational amplifier for sampling.

[0003] However, if sampling is performed using isolated op amp chips or linear optocouplers, the manufacturing process of isolated op amp chips is complex, and they integrate isolation components and high-precision op amps, resulting in relatively high costs. In particular, some high-performance, high-isolation voltage isolated op amp chips can be quite expensive. While linear optocouplers may be slightly cheaper than some isolated op amp chips, their cost is still relatively high compared to ordinary electronic components.

[0004] If high-impedance (at least six 1MΩ resistors in series) op amps are used for sampling, high-impedance isolation may not provide adequate isolation in some cases. For example, when a system experiences large common-mode voltages or high-frequency interference, the high-impedance resistors may not effectively block the interference signal, compromising the accuracy of the sampled signal. In areas such as industrial control and medical equipment, where isolation performance is critical, this high-impedance isolation solution may not meet safety and reliability requirements. The presence of high-impedance resistors increases the circuit's input impedance, making it susceptible to external environmental noise, such as static interference and electromagnetic radiation. This can introduce noise into the sampled signal, degrading signal quality.

[0005] In summary, although isolated sampling circuits using isolated op amp chips or linear optocouplers are fully isolated, they come at the expense of component cost. Isolated sampling circuits using high-impedance (at least six 1MΩ op amps in series) are high-impedance isolation circuits and may not provide adequate isolation in some situations. Utility Model Content

[0006] The embodiments of the present application provide a voltage follower circuit and a voltage follower, which have simple circuit elements, low cost, achieve complete isolation, and accurately implement voltage following, thereby improving the stability and anti-interference ability of voltage following.

[0007] In the first aspect, an embodiment of the present application provides a voltage follower circuit, which includes an operational amplifier module, a first voltage divider module, a second voltage divider module, an isolation module, a feedback module, a first power supply, a second power supply, and a third power supply; wherein, the first power supply and the third power supply share a common ground, and the first power supply and the second power supply do not share a common ground; the non-phase input terminal of the operational amplifier module is connected to the first power supply, the inverting input terminal of the operational amplifier module is connected to the first ground through the first voltage divider module, the output terminal of the operational amplifier module is connected to the first ground through the isolation module and the feedback module, the isolation module is also connected to the second power supply, the isolation module is also connected to the second ground through the second voltage divider module, and the feedback module It is also connected to the third power supply, and the feedback module is also connected to the inverting input terminal of the operational amplifier module; the operational amplifier module is used to output a first current signal when receiving the input voltage of the first power supply; the feedback module is used to output a feedback voltage when receiving the first current signal and the third power supply is powered, so that the operational amplifier module enters a virtual short state, so that the feedback voltage is equal to the input voltage; the isolation module is used to output a target voltage when receiving the first current signal and the second power supply is powered; wherein the resistance value of the first voltage divider module and the resistance value of the second voltage divider module are configured to be equal, so that the target voltage is equal to the feedback voltage, that is, the target voltage is equal to the input voltage.

[0008] In some embodiments, the operational amplifier module includes an amplifier U1; the non-inverting input terminal of the amplifier U1 is connected to the first power supply, the inverting input terminal of the amplifier U1 is connected to the first ground through the first voltage divider module, the output terminal of the amplifier U1 is connected to the first ground through the isolation module and the feedback module, and the feedback module is also connected to the inverting input terminal of the amplifier U1.

[0009] In some embodiments, the operational amplifier module further includes a resistor R1 and a resistor R2; the first end of the resistor R1 is connected to the first end of the resistor R2 and the first power supply, the second end of the resistor R1 is connected to the non-inverting input terminal of the amplifier U1, and the second end of the resistor R2 is connected to the first ground.

[0010] In some embodiments, the first voltage divider module includes a resistor R3; a first end of the resistor R3 is connected to the inverting input end of the operational amplifier module and the feedback module, and a second end of the resistor R3 is connected to the first ground.

[0011] In some embodiments, the first voltage divider module further includes a capacitor C1; the capacitor C1 is connected in parallel with the resistor R3.

[0012] In some embodiments, the isolation module includes an optocoupler K1; the positive electrode of the light-emitting diode of the optocoupler K1 is connected to the output end of the operational amplifier module, the negative electrode of the light-emitting diode of the optocoupler K1 is connected to the first ground through the feedback module, the collector of the phototransistor of the optocoupler K1 is connected to the second power supply, and the emitter of the phototransistor of the optocoupler K1 is connected to the second ground through the second voltage divider module.

[0013] In some embodiments, the feedback module includes an optocoupler K2; the positive electrode of the light-emitting diode of the optocoupler K2 is connected to the output end of the operational amplifier module through the isolation module, the negative electrode of the light-emitting diode of the optocoupler K2 is connected to the first ground, the collector of the phototransistor of the optocoupler K2 is connected to the third power supply, and the emitter of the phototransistor of the optocoupler K2 is connected to the inverting input end of the operational amplifier module.

[0014] In some embodiments, the second voltage divider module includes a resistor R4 ; a first end of the resistor R4 is connected to the emitter of the phototransistor of the optical coupler K1 , and a second end of the resistor R4 is connected to the second ground.

[0015] In some embodiments, the second voltage divider module further includes a capacitor C2; the capacitor C2 is connected in parallel with the resistor R4.

[0016] In a second aspect, an embodiment of the present application provides a voltage follower, which includes the voltage follower circuit as described above.

[0017] Different from the related technical solutions, the embodiment of the present application provides a voltage following circuit and a voltage follower. In the embodiment of the present application, since the first power supply and the second power supply do not share a common ground, and the signal is transmitted through the isolation module, electrical isolation between different power domains is achieved. This can reduce problems such as ground loop current and common mode interference between different power supply systems. For example, in a complex mixed signal system, when the digital power supply and the analog power supply do not share a common ground, the circuit can ensure that the signal is stably transmitted between different power domains without mutual interference. The operational amplifier module is put into a virtual short state through the feedback module, ensuring that the feedback voltage is equal to the input voltage. At the same time, the configuration of the first voltage divider module and the second voltage divider module with equal resistance values makes the target voltage equal to the feedback voltage, thereby achieving precise voltage following. At the same time, the circuit elements are simpler, the cost is lower, and complete isolation is achieved, and voltage following is accurately achieved, which improves the stability and anti-interference ability during voltage following. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] One or more embodiments are exemplarily described by corresponding drawings, which do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0019] Figure 1 This is a structural block diagram of a voltage follower circuit provided in one embodiment of the present application;

[0020] Figure 2 Schematic diagram of the circuit structure of a voltage follower circuit provided in one embodiment of the present application. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0022] The technical features involved in the various embodiments of the present application described below do not conflict with each other and can be combined with each other.

[0023] When an element is referred to as being “connected to” another element, it can be directly connected to the other element, or one or more intervening elements may be present therebetween.

[0024] The terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of this application can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "first," "second," and the like generally distinguish objects of a class and do not limit the number of objects. For example, the first object may be one or more.

[0025] See also Figure 1 , Figure 1 1 is a structural block diagram of a voltage follower circuit 100 provided in one embodiment of the present application.

[0026] The voltage follower circuit 100 provided in an embodiment of the present application includes an operational amplifier module 11, a first voltage divider module 12, a second voltage divider module 13, an isolation module 14, a feedback module 15, a first power supply VAA, a second power supply VBB, and a third power supply VCC; wherein the first power supply VAA and the third power supply VCC share a common ground, and the first power supply VAA and the second power supply VBB do not share a common ground.

[0027] Among them, the non-inverting input terminal of the operational amplifier module 11 is connected to the first power supply VAA, the inverting input terminal of the operational amplifier module 11 is connected to the first ground GNDA through the first voltage divider module 12, the output terminal of the operational amplifier module 11 is connected to the first ground GNDA through the isolation module 14 and the feedback module 15, the isolation module 14 is also connected to the second power supply VBB, the isolation module 14 is also connected to the second ground GNDB through the second voltage divider module 13, the feedback module 15 is also connected to the third power supply VCC, and the feedback module 15 is also connected to the inverting input terminal of the operational amplifier module 11.

[0028] Specifically, the operational amplifier module 11 is configured to output a first current signal upon receiving an input voltage VAA from a first power supply VAA. The feedback module 15 is configured to output a feedback voltage V1 upon receiving the first current signal and powered by a third power supply VCC, causing the operational amplifier module 11 to enter a virtual short state, such that the feedback voltage V1 is equal to the input voltage VAA. The isolation module 14 is configured to output a target voltage Vref upon receiving the first current signal and powered by a second power supply VBB. The resistance values of the first voltage divider module 12 and the second voltage divider module 13 are configured to be equal, such that the target voltage Vref is equal to the feedback voltage V1, i.e., the target voltage Vref is equal to the input voltage VAA.

[0029] In practical applications, first, when there is an input voltage VAA, the operational amplifier module 11 amplifies the input signal to output a first current signal. In this process, the amplification factor of the operational amplifier module 11 depends on its internal structure and external feedback circuit.

[0030] Then, the feedback module 15 starts to work when it receives the first current signal and the third power supply VCC from the operational amplifier module 11. It generates a feedback voltage V1 through a circuit network composed of internal components according to the input current signal and power supply.

[0031] Then, the feedback voltage V1 output by the feedback module 15 is fed back to the inverting input terminal of the operational amplifier module 11, causing the operational amplifier module 11 to enter a virtual short state. In this state, the feedback voltage V1 is equal to the input voltage VAA of the non-inverting input terminal of the operational amplifier module 11.

[0032] Simultaneously, isolation module 14 receives the first current signal and the second power supply VBB from op amp module 11. Its primary function is to electrically isolate the two power domains where the first power supply VAA and the second power supply VBB reside. While isolating the power domains, it converts the received current signal into a target voltage Vref for output.

[0033] Furthermore, the isolation module 14 is connected to the second ground GNDB via the second voltage divider module 13. Since the resistance values of the first voltage divider module 12 and the second voltage divider module 13 are configured to be equal, according to the voltage divider principle, under ideal conditions, the target voltage Vref output by the isolation module 14 is equal to the feedback voltage V1 output by the feedback module 15, thereby achieving a voltage following effect in which the target voltage Vref is equal to the input voltage VAA.

[0034] Furthermore, the first voltage divider module 12 is connected between the inverting input terminal of the operational amplifier module 11 and the first ground GNDA, and serves to divide and adjust the potential of the inverting input terminal of the operational amplifier module 11. By properly setting its resistance value, it can cooperate with the feedback module 15 to put the operational amplifier module 11 into a virtual short state.

[0035] In this embodiment, the second voltage divider module 13 works in conjunction with the isolation module 14 to divide the signal output by the isolation module 14. Since its resistance is equal to that of the first voltage divider module 12, the consistency of the target voltage Vref and the feedback voltage V1 is ensured in different power domains, thus realizing the transmission of the voltage following function in different power domains.

[0036] Furthermore, the first power supply VAA provides the input voltage VAA for the operational amplifier module 11 and is the source of the entire circuit signal. The third power supply VCC powers the feedback module 15, ensuring that the feedback module can operate normally and generate the feedback voltage V1, causing the operational amplifier module 11 to enter a virtual short state. They share a common ground, providing a stable potential reference point for this part of the circuit. The second power supply VBB powers the isolation module 14, enabling the isolation module to transmit signals and electrically isolate between different power domains while ensuring the stability of the output target voltage Vref.

[0037] See also Figure 2 , Figure 2 1 is a schematic diagram of the circuit structure of a voltage follower circuit 100 provided in an embodiment of the present application.

[0038] In some embodiments, the operational amplifier module 11 includes an amplifier U1 .

[0039] Among them, the non-inverting input terminal of the amplifier U1 is connected to the first power supply VAA, the inverting input terminal of the amplifier U1 is connected to the first ground GNDA through the first voltage divider module 12, and the output terminal of the amplifier U1 is connected to the first ground GNDA through the isolation module 14 and the feedback module 15. The feedback module 15 is also connected to the inverting input terminal of the amplifier U1.

[0040] In some embodiments, the operational amplifier module 11 further includes a resistor R1 and a resistor R2.

[0041] The first end of the resistor R1 is connected to the first end of the resistor R2 and the first power supply VAA, the second end of the resistor R1 is connected to the non-inverting input end of the amplifier U1, and the second end of the resistor R2 is connected to the first ground GNDA.

[0042] Specifically, resistors R1 and R2 form a voltage divider circuit that divides the voltage between the first power supply VAA and the first ground GNDA to generate a bias voltage, which is applied to the non-inverting input of amplifier U1. This establishes an initial quiescent operating point for the amplifier, ensuring that it processes input signals within its proper operating range.

[0043] In some embodiments, the first voltage dividing module 12 includes a resistor R3 .

[0044] The first end of the resistor R3 is connected to the inverting input terminal of the operational amplifier module 11 and the feedback module 15 , and the second end of the resistor R3 is connected to the first ground GNDA.

[0045] In some embodiments, the first voltage dividing module 12 further includes a capacitor C1 .

[0046] The capacitor C1 is connected in parallel with the resistor R3.

[0047] In some embodiments, the feedback module 15 includes an optical coupler K2 .

[0048] Among them, the positive electrode of the light-emitting diode of the optical coupler K2 is connected to the output end of the operational amplifier module 11 through the isolation module 14, the negative electrode of the light-emitting diode of the optical coupler K2 is connected to the first ground GNDA, the collector of the phototransistor of the optical coupler K2 is connected to the third power supply VCC, and the emitter of the phototransistor of the optical coupler K2 is connected to the inverting input end of the operational amplifier module 11.

[0049] In some embodiments, the isolation module 14 includes an optical coupler K1 .

[0050] Among them, the positive electrode of the light-emitting diode of the optocoupler K1 is connected to the output end of the operational amplifier module 11, the negative electrode of the light-emitting diode of the optocoupler K1 is connected to the first ground GNDA through the feedback module 15, the collector of the phototransistor of the optocoupler K1 is connected to the second power supply VBB, and the emitter of the phototransistor of the optocoupler K1 is connected to the second ground GNDB through the second voltage divider module 13.

[0051] Optocoupler K1 and optocoupler K2 can be of the same parameters and / or model. The current output by amplifier U1 flows through both optocoupler K1 and optocoupler K2 simultaneously, so the output currents of optocoupler K1 and optocoupler K2 should be equal.

[0052] In some embodiments, the second voltage dividing module 13 includes a resistor R4 .

[0053] A first end of the resistor R4 is connected to the emitter of the phototransistor of the optical coupler K1 , and a second end of the resistor R4 is connected to the second ground GNDB.

[0054] In some embodiments, the second voltage dividing module 13 further includes a capacitor C2.

[0055] The capacitor C2 is connected in parallel with the resistor R4.

[0056] In some embodiments, the resistance of the resistor R3 is equal to the resistance of the resistor R4.

[0057] In some embodiments, the first power supply VAA and the third power supply VCC share a common ground, while the first power supply VAA and the second power supply VBB do not share a common ground and are isolated from each other. The voltages of the first power supply VAA, the second power supply VBB, and the third power supply VCC do not necessarily need to be equal.

[0058] In some embodiments, when the voltage of the first power supply VAA is equal to the voltage of the third power supply VCC, the output can be more accurate.

[0059] The following Figure 2 The principle of the circuit structure shown is explained again.

[0060] First, after the input voltage VAA enters the non-inverting input terminal of the amplifier U1, the amplifier U1 amplifies the signal according to its internal gain and the potential difference between the non-inverting input terminal and the inverting input terminal.

[0061] The output signal of amplifier U1 is then fed back to the inverting input via isolation module 14 and feedback module 15. Specifically, feedback module 15, comprised of optocoupler K2, feeds back changes in the output signal to the inverting input of amplifier U1. The parallel network consisting of capacitor C1 and resistor R3 filters and stabilizes the feedback signal at the inverting input. In a stable state, this feedback causes amplifier U1 to enter a virtual short state, where the potentials at the non-inverting and inverting inputs are nearly equal, thereby achieving stable amplification of the input signal.

[0062] At the same time, the isolation module 14 composed of the optocoupler K1 plays a key role in electrical isolation and signal transmission. The output signal of amplifier U1 causes the light-emitting diode of optocoupler K1 to emit light, and the intensity of the light emission is related to the output signal strength of amplifier U1. After receiving the light signal, the phototransistor converts the light signal into a current signal and transmits it between the second power supply VBB and the second ground GNDB. This method of signal transmission via optical signals achieves electrical isolation between the first power domain (including the op amp module 11, etc.) and the second power domain.

[0063] At this point, the signal output by the isolation module 14 passes through the second voltage divider module 13. The second voltage divider module 13, consisting of a resistor R4 and a capacitor C2 in parallel, divides and filters the signal output by the isolation module 14. Resistor R4 divides the signal based on the potential relationship between the resistor R4, the equivalent resistance within the optocoupler K1, and the second power supply VBB and the second ground GNDB. Capacitor C2 filters high-frequency noise in the output signal.

[0064] Since the resistance of resistor R3 in the first voltage divider module 12 is equal to the resistance of resistor R4 in the second voltage divider module 13, and the feedback module 15 causes amplifier U1 to enter a virtual short state, the entire circuit implements a voltage following function. That is, the input voltage of the first power supply VAA input to the operational amplifier module 11 changes, and after a series of amplification, isolation, feedback, and voltage division processes, the target voltage Vref output in the second power domain is equal to the input voltage VAA. This allows the circuit to transmit voltage signals between different power domains while maintaining signal accuracy and stability, and effectively avoids electrical interference between different power domains.

[0065] In summary, an embodiment of the present application provides a voltage follower circuit 100. In the embodiment of the present application, since the first power supply and the second power supply do not share a common ground, and signal transmission is performed through an isolation module, electrical isolation between different power domains is achieved. This can reduce problems such as ground loop current and common mode interference between different power supply systems. For example, in a complex mixed signal system, when the digital power supply and the analog power supply do not share a common ground, the circuit can ensure that the signal is stably transmitted between different power domains without mutual interference. The operational amplifier module is put into a virtual short state through the feedback module, ensuring that the feedback voltage is equal to the input voltage. At the same time, the configuration of the first voltage divider module and the second voltage divider module with equal resistance values makes the target voltage equal to the feedback voltage, thereby achieving accurate voltage following. At the same time, the circuit elements are simpler, the cost is lower, and complete isolation is achieved, and voltage following is accurately achieved, which improves the stability and anti-interference ability during voltage following.

[0066] The embodiment of the present application further provides a voltage follower, which includes the voltage follower circuit 100 as described above.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Under the idea of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the present invention as described above. For the sake of simplicity, they are not provided in detail. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the above embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A voltage follower circuit, characterized in that: The voltage follower circuit includes an operational amplifier module, a first voltage divider module, a second voltage divider module, an isolation module, a feedback module, a first power supply, a second power supply, and a third power supply; wherein the first power supply and the third power supply share a common ground, and the first power supply and the second power supply do not share a common ground; The non-inverting input terminal of the operational amplifier module is connected to the first power supply, the inverting input terminal of the operational amplifier module is connected to the first ground through the first voltage divider module, the output terminal of the operational amplifier module is connected to the first ground through the isolation module and the feedback module, the isolation module is also connected to the second power supply, the isolation module is also connected to the second ground through the second voltage divider module, the feedback module is also connected to the third power supply, and the feedback module is also connected to the inverting input terminal of the operational amplifier module; The operational amplifier module is configured to output a first current signal upon receiving an input voltage from the first power supply; The feedback module is configured to output a feedback voltage to put the operational amplifier module into a virtual short state when receiving the first current signal and the third power supply is supplied, so that the feedback voltage is equal to the input voltage; The isolation module is configured to output a target voltage when receiving the first current signal and the second power supply is powered; The resistance value of the first voltage divider module and the resistance value of the second voltage divider module are configured to be equal, so that the target voltage is equal to the feedback voltage, that is, the target voltage is equal to the input voltage.

2. The voltage follower circuit according to claim 1, wherein: The operational amplifier module includes an amplifier U1; The non-inverting input terminal of the amplifier U1 is connected to the first power supply, the inverting input terminal of the amplifier U1 is connected to the first ground through the first voltage divider module, the output terminal of the amplifier U1 is connected to the first ground through the isolation module and the feedback module, and the feedback module is also connected to the inverting input terminal of the amplifier U1.

3. The voltage follower circuit according to claim 2, wherein: The operational amplifier module further includes a resistor R1 and a resistor R2; The first end of the resistor R1 is connected to the first end of the resistor R2 and the first power supply, the second end of the resistor R1 is connected to the non-inverting input end of the amplifier U1, and the second end of the resistor R2 is connected to the first ground.

4. The voltage follower circuit according to claim 1, wherein: The first voltage dividing module includes a resistor R3; A first end of the resistor R3 is connected to the inverting input end of the operational amplifier module and the feedback module, and a second end of the resistor R3 is connected to the first ground.

5. The voltage follower circuit according to claim 4, characterized in that: The first voltage dividing module further includes a capacitor C1; The capacitor C1 is connected in parallel with the resistor R3.

6. The voltage follower circuit according to claim 1, wherein: The isolation module includes an optical coupler K1; The anode of the light-emitting diode of the optocoupler K1 is connected to the output end of the operational amplifier module, the cathode of the light-emitting diode of the optocoupler K1 is connected to the first ground through the feedback module, the collector of the phototransistor of the optocoupler K1 is connected to the second power supply, and the emitter of the phototransistor of the optocoupler K1 is connected to the second ground through the second voltage divider module.

7. The voltage follower circuit according to claim 1, wherein: The feedback module includes an optical coupler K2; The positive electrode of the light-emitting diode of the optical coupler K2 is connected to the output end of the operational amplifier module through the isolation module, the negative electrode of the light-emitting diode of the optical coupler K2 is connected to the first ground, the collector of the phototransistor of the optical coupler K2 is connected to the third power supply, and the emitter of the phototransistor of the optical coupler K2 is connected to the inverting input end of the operational amplifier module.

8. The voltage follower circuit according to claim 6, wherein: The second voltage dividing module includes a resistor R4; A first end of the resistor R4 is connected to the emitter of the phototransistor of the optical coupler K1 , and a second end of the resistor R4 is connected to the second ground.

9. The voltage follower circuit according to claim 8, characterized in that: The second voltage dividing module further includes a capacitor C2; The capacitor C2 is connected in parallel with the resistor R4.

10. A voltage follower, characterized in that: The voltage follower comprises the voltage follower circuit according to any one of claims 1 to 9.

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