Current amplifier

Abstract

The utility model discloses a current amplifier, and belongs to the field of photoelectric detection pre-amplification. The current amplifier comprises a direct current bias conversion module, an input stage amplification module and a differential voltage amplification module which are cascaded in sequence. The direct current bias conversion module is used for converting direct current bias voltage into direct current bias current, and the input stage amplification module is used for converting the direct current bias current and input current into differential alternating current voltage and outputting the differential alternating current voltage to the differential voltage amplification module. The differential voltage amplification module is used for gaining or attenuating the differential alternating-current voltage and then outputting the differential alternating-current voltage; according to the utility model, by adjusting the bias voltage of the constant current source formed by the transistors, the gain can be independently controlled, and the problem that the gain of the current amplifier formed by the integrated operational amplifier cannot be independently controlled is solved; the complexity of circuit design is avoided, and the problem that parasitic parameters are additionally introduced due to the fact that a current amplifier formed by an integrated operational amplifier is cascaded with a controllable gain amplifier is avoided.

Description

TECHNICAL FIELD

[0001] The utility model relates to a current amplifier belongs to photoelectric detection preamplification field. BACKGROUND

[0002] The current amplifier is used for amplifying input current to required current or voltage intensity, while keeping the phase and frequency characteristics of the signal unchanged. It is widely used in sensor and photoelectric device signal processing field, such as weak current signal amplification of pressure sensor, electrochemical sensor, and linear amplification of photodiode and photomultiplier output signal.

[0003] With the rapid development of precision measurement technology, the observation scale of physical quantities in engineering field is continuously reduced. In order to facilitate unified processing, accurate analysis and subsequent observation of these physical quantities, in addition to electricity, other types of physical quantities (such as light intensity, force, temperature, pressure, displacement, acceleration, etc.) also need to be converted into electrical signals for processing through sensors or measuring devices. However, the signal generated by small-scale measurement is often extremely weak and easily disturbed by background noise, so a high-gain, low-noise amplifier is needed to effectively extract the signal. Based on this demand, to ensure that the phase and frequency information between the output signal and the input signal remains consistent or related under the above conditions, while ensuring that the amplifier structure has customizability and flexibility (can adapt to diversified physical quantity input types) on the basis of universality, this is the current problem to be solved.

[0004] In some related technical applications, integrated operational amplifiers are usually selected as the core of the current amplifier for occasions requiring current amplification or conversion. Such devices are widely used due to their convenient application and fewer peripheral circuit components. Especially when combined with high-precision peripheral components, integrated operational amplifiers can provide relatively stable gain. However, as a "black box" design, the internal circuit of the integrated operational amplifier cannot be adjusted, making it difficult to optimize flexibly according to specific needs. In addition, during circuit design, complex calculations, simulations and tests are usually required to ensure the stability of the system feedback loop. For some integrated operational amplifiers with internal compensation, not only the stability of the external feedback loop needs to be ensured, but also the internal stability needs to be considered, which undoubtedly increases the design difficulty.

[0005] In pressure sensor output signal amplification applications, a high-precision integrated operational amplifier (such as TI's OPA211, typical open-loop gain 120dB) can provide stable current amplification. However, due to the internal compensation circuit, the design of the feedback network needs to meet the strict requirements of phase margin and gain margin, otherwise it may cause oscillation or signal distortion. When the phase margin is lower than 45° due to improper feedback loop design, the system stability will decrease significantly.

[0006] In particle detection equipment (such as a secondary electron detector, a particle accelerator), the output signal of a photomultiplier tube (PMT) is a fast and weak pulse current signal, which needs to be accurately amplified and the pulse waveform characteristics need to be maintained. Using a high-speed operational amplifier (such as OPA847) can provide preliminary signal amplification, but the limitation of the impulse response will cause the signal to lose phase and frequency information. To avoid this situation, designers need to add a transistor front-end circuit before the operational amplifier to improve the bandwidth and transient response capability of the input stage, and also need to optimize impedance matching, adjust feedback control or introduce dynamic feedback control. But this greatly increases the complexity and risk of circuit design.

[0007] In audio signal processing (such as front-end amplification of a condenser microphone), the amplitude of the input signal varies greatly, which may span several tens of dB from low to high. In order to ensure the constant amplitude of the output signal, the gain of the current amplifier needs to be adjusted in real time. Integrated operational amplifiers can only provide fixed gain in this scenario. If the amplitude of the input signal exceeds the design range, it may cause nonlinear distortion of high-intensity audio signals or failure to amplify low-intensity signals. The gain needs to be adjusted in real time according to the amplitude of the input signal, which is usually achieved by cascading additional dynamic control circuits or dedicated AGC modules. The internal circuit structure of the integrated operational amplifier determines that it cannot complete this real-time gain adjustment alone. When cascading dynamic control circuits or dedicated AGC modules, additional parasitic parameters are introduced into the entire amplification system, further increasing the difficulty of design and debugging. Practical new type content

[0008] In order to expand the application range of the circuit amplifier, improve the flexibility of application, realize gain adjustment, and avoid complex debugging process in the application process and reduce the use cost, the utility model provides a current amplifier, and the technical scheme is as follows.

[0009] The current amplifier of the utility model comprises a direct current bias conversion module, an input stage amplification module and a differential voltage amplification module which are cascaded in sequence, the direct current bias conversion module is used for converting a direct current bias voltage into a direct current bias current, the input stage amplification module is used for converting the direct current bias current and an input current into a differential alternating voltage and outputting to the differential voltage amplification module, and the differential voltage amplification module is used for outputting after gain or attenuation of the differential alternating voltage.

[0010] The input stage amplification module comprises: triode Q10A, triode Q10B, switch diode V2A, switch diode V2B, Zener diode V3, DC zero resistance network, first constant current source, constant current circuit with current buffer; the triode Q10A and the triode Q10B are a pair of packaged PNP small signal triodes, which constitute a differential input pair of a differential amplifier; the base of the triode Q10A is grounded, the emitter is connected to the first constant current source through the resistor R21, and the collector is connected with the anode of the switch diode V2A; the base of the triode Q10B is connected with the current input end, the emitter is connected with the DC zero resistance network, and the collector is connected with the anode of the switch diode V2B; the switch diode V2A, the switch diode V2B and the Zener diode V3 constitute an output DC clamping circuit; the constant current circuit with current buffer comprises a resistor R29, a resistor R30, a resistor R38, a triode Q7 and a triode Q11, a gain control voltage input port is connected to the base of the triode Q11 through the resistor R29 and the resistor R30, and one end of the resistor R29 and the resistor R30 is grounded through the capacitor C6; the emitter of the triode Q11 is grounded, and the collector is connected with the emitter of the triode Q7; the base of the triode Q7 is grounded, and the collector is connected with the first constant current source.

[0011] The differential voltage amplification module comprises: a switch diode pair V1, a switch diode D1, a NPN small signal triode pair Q1A and Q1B, and a second constant current source; the switch diode pair V1 and the switch diode D1 constitute a DC voltage clamping circuit of a differential output of a stage amplifier; the differential alternating voltage is input through two bases of the NPN small signal triode pair Q1A and Q1B; two emitters of the NPN small signal triode pair Q1A and Q1B are connected with the second constant current source, two collectors are respectively connected with a power supply through a resistor R1, a resistor R3, a resistor R2 and a resistor R4, and the output differential voltage is output from one end of the resistor R1 and the resistor R3 and one end of the resistor R2 and the resistor R4.

[0012] In an embodiment, the DC zero resistance network comprises: a resistor R15, a resistor R22 and a resistor R18; the resistor R15 and the resistor R18 are connected in parallel and then connected in series with the resistor R22, one end of the resistor R15 and the resistor R18 is connected with one end of the second constant current source and the constant current circuit with current buffer, and the other end of the resistor R22, which is not connected with the resistor R18 and the resistor R15, is connected with the emitter of the triode Q10B.

[0013] In one embodiment, the first constant current source comprises: a resistor R10, a resistor R11, a resistor R14 and a transistor Q3; the emitter of the transistor Q3 is connected with a power supply through the resistor R10, the collector is connected with the constant current circuit of the current buffer, the emitter resistor of the transistor Q10A and the DC zeroing resistor network of the transistor Q10B respectively, and the base is connected with one end of the resistor R11 and the resistor R14.

[0014] In one embodiment, the second constant current source comprises: a transistor Q2, a resistor R8 and a resistor R9, the base of the transistor Q2 is connected with a gain control voltage input end GAIN, the emitter is connected with a -9V power supply through the resistor R9, and the collector is connected with the emitter of the NPN small signal transistor pair Q1A and Q1B.

[0015] In one embodiment, the cathodes of the switching diode V2A and the switching diode V2B are connected with a resistor R42 and the anode of a Zener diode V3 respectively, the other end of the resistor R42 is connected with a -9V power supply, and the cathode of the Zener diode V3 is grounded.

[0016] In one embodiment, the two anodes of the switching diode pair V1 are connected with one end of the resistor R1 and the resistor R3, one end of the resistor R2 and the resistor R4 respectively, the cathode is connected with the anode of the switching diode D1, and the cathode of the switching diode D1 is grounded.

[0017] In one embodiment, the DC bias conversion module comprises a resistor R5, a resistor R6, a resistor R7, a capacitor C1 and a capacitor C2, the resistor R5, the resistor R6 and the resistor R7 are connected in sequence, the input end of the resistor R5 is connected with an amplifier DC voltage bias input interface, and the output end of the resistor R7 is connected with a current input end IN; one end of the capacitor C1 is connected with one end of the resistor R5 and the resistor R6, and the other end is grounded; one end of the capacitor C2 is connected with one end of the resistor R6 and the resistor R7, and the other end is grounded.

[0018] The current amplifier has the following advantages:

[0019] The current amplifier does not need to design a loop outside the circuit structure, gain adjustment is carried out by adjusting the input voltage of the transistor, the amplification mode is open-loop amplification, the complex calculation and debugging process in the application process of the integrated amplifier is effectively avoided, and the stability of signal extraction and amplification is ensured.

[0020] The current amplifier has high flexibility, can adapt to a wide current input range and a noise range matched with current intensity by replacing input side transistors, can realize amplifier bandwidth expansion by changing circuit structure, and can realize amplifier bandwidth controllability by adjusting output side collector electrode capacitors.

[0021] The current amplifier provided by the utility model realizes that the gain is individually controllable, solves the problem that the current amplifier composed of integrated operational amplifiers cannot control the gain individually, and avoids the complexity of circuit design and the problem that the current amplifier composed of integrated operational amplifiers introduces parasitic parameters additionally. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structure diagram of the direct current bias conversion module in the embodiment 1.

[0023] Figure 2 It is a structure diagram of the input stage amplification module in the embodiment 1.

[0024] Figure 3 It is a structure diagram of the differential voltage amplification module in the embodiment 1.

[0025] Figure 4 It is a waveform diagram of the output interface when inputting 10uApeak 5ns pulse width and 200ns continuous pulse signals in the embodiment 2.

[0026] Figure 5 It is a waveform diagram of the output interface when inputting 160uApeak 5ns pulse width and 200ns continuous pulse signals in the embodiment 2.

[0027] Figure 6 It is a voltage output waveform observed at the output end of the integrated operational amplifier in the embodiment 2.

[0028] Figure 7 It is a gain and frequency curve diagram of the current amplifier when BIAS input is grounded and GAIN input is-4.8V direct current level in the embodiment 3.

[0029] Figure 8 It is a gain and frequency curve diagram of the current amplifier when BIAS input is grounded and GAIN input is-5.3V direct current level in the embodiment 3.

[0030] Figure 9 It is a gain and frequency curve diagram of the current amplifier when BIAS input is grounded and GAIN input is-5.8V direct current level in the embodiment 3.

[0031] Figure 10This is a graph showing the gain and frequency of the current amplifier when the BIAS input is grounded and the GAIN input is at a DC level of -6.3V in Example 3.

[0032] Figure 11 This is a graph showing the gain and frequency of the current amplifier when the BIAS input is grounded and the GAIN input is at a DC level of -6.8V in Example 3.

[0033] Figure 12 This is a graph showing the gain of the current amplifier versus the absolute value of the DC level at the GAIN input terminal in Example 3. Detailed Implementation

[0034] The following is a detailed description of this utility model.

[0035] Example 1:

[0036] This embodiment provides a current amplifier, including a cascaded DC bias conversion module, an input stage amplification module, and a differential voltage amplification module. The DC bias conversion module is used to convert DC bias voltage into DC bias current. The input stage amplification module is used to convert the input current into a differential AC voltage and output it to the differential voltage amplification module. The differential voltage amplification module amplifies or attenuates the input differential voltage before outputting it.

[0037] First, the external interface of the circuit will be described. Figure 1 and Figure 2 IN, as shown, is the amplifier current signal input interface. Figure 1 BIAS in the diagram refers to the amplifier's DC voltage bias input interface. Figure 2 , Figure 3 The GAIN shown is the amplifier gain control voltage interface.

[0038] like Figure 3 As shown, S2+ is the positive signal output interface of the amplifier, and S2- is the negative signal output interface of the amplifier. S2+ and S2- form a set of differential output interfaces.

[0039] The structure of the DC bias conversion module is as follows: Figure 1 As shown, resistors R5, R6, and R7, and capacitors C1 and C2 form a low-pass filter to limit the noise bandwidth of the DC voltage input.

[0040] The structure of the input stage amplifier module is as follows: Figure 2 As shown, this stage amplifier converts the single-ended AC current into a differential AC voltage output to the next stage.

[0041] Q10 is a pair of PNP small signal transistors in package, which constitute the differential input pair and the basic amplification structure of the differential amplifier, V2 (V2A and V2B) is a pair of packaged switching diodes, V3 is a Zener diode, V2-V3 constitute the output DC clamping circuit of the stage amplifier, and provide the input static operating point voltage for the next stage. R21 and R22 are the emitter resistors of Q10, which provide the static operating point voltage for Q10. R15, R18, R22 are the DC zeroing resistance network of the differential output terminal of the stage amplifier. R10, R11, R14, Q3 constitute the constant current source of the differential amplifier. R25 is connected to the inverting input terminal Q10A 1 pin of the stage amplifier, and balances the DC voltage of the differential input, the resistance value of R25 is equal to the sum of R26 and R23, R23 is connected in series with R26 to the non-inverting terminal of the stage amplifier as the base bias balancing resistor of the non-inverting terminal Q10B 2 pin, so the sum of the resistance values of R26 and R23 is equal to R25. Q7, Q11, R29, R30 and R38 constitute the constant current circuit with current buffer, which has the function of adjusting the gain of the stage amplifier with GAIN voltage, wherein R29, C6 and R30 constitute a low-pass filter, which filters out the AC component on the DC and limits the bandwidth to reduce noise introduction. C5 and the output impedance of the IN input side constitute a low-pass filter, which smooths the pulse output of the sensing and detecting device in the case of slow amplification. R33 is connected to the collector of Q10A 6 pin at one end and to the -9V power supply at the other end, which provides the static operating point for the amplification circuit. R34 is connected to the collector of Q10B 3 pin at one end and to the -9V power supply at the other end, which provides the static operating point for the amplification circuit.

[0042] The working principle (signal flow direction) of the input stage amplification module is as follows: a current signal is input from the port IN, and is converted into an input voltage signal through a R23 current collection resistor and a C5 pulse smoothing capacitor. The input voltage signal is input to the base of Q10B 2, and a current signal in a fixed proportional relationship with the input voltage signal and in phase is output from the collector of Q10B 3, and is smoothed through a R34 resistor, and a voltage signal opposite to the input voltage signal is obtained at the collector of Q10B 3. Due to the constant current characteristic of Q3 as the core component of the constant current source, the sum of the currents output from the collector of Q10B 3 and the collector of Q10A 6 is constant, and a current signal of the same intensity and opposite phase as the current output from the collector of Q10B 3 is output from the collector of Q10A 6. Similarly, a voltage signal in phase with the input voltage is obtained at the collector of Q10A 6. The voltage signals output from the collector of Q10A 6 and the collector of Q10B 3 are of the same intensity and opposite phase, and constitute a pair of complementary differential signals. When the complementary differential signals are unbalanced, R18 is adjusted, so that the resistance value of R15 in parallel with R18 plus the resistance value of R22 is equal to the resistance value of R21. The DC level is fixed under the action of the output DC clamping circuit, and the DC level fixing has the static bias voltage of the input port of the differential voltage amplification module S1-S1+.

[0043] A current signal is input from the port IN, and is converted into a voltage signal through a R23 current collection resistor and a C5 pulse smoothing capacitor. The voltage signal is input to the base of Q10B 2, and is output from the collector of Q10A 6 and the collector of Q10B 3 to the ports S1- and S1+ after being amplified by the differential amplifier circuit composed of Q10 as the core component of the input stage amplification module.

[0044] The GAIN DC voltage signal passes through a low-pass filter composed of R29, C6 and R30, and is input to the collector of Q11 of the constant current source with a current buffer. The GAIN DC voltage signal is proportional to the current of the constant current source, so as to control the DC current intensity of the constant current source composed of Q3 as the core component, and further control the gain of the input stage amplification module.

[0045] The gain adjustment DC voltage signal is input from port GAIN, and is input to the base of Q111 through R29, C6 and R30. Q11 and R38 form a voltage-controlled constant current source. The DC current intensity output from the collector of Q113 is in fixed proportion to the DC voltage intensity of the GAIN port. The DC current intensity of the collector of Q113 and the collector of Q73 is of the same polarity, so that the GAIN DC voltage controls the DC current of the collector of Q73 in proportion. The collector of Q73 and the collector of Q3 are connected to the same node NODE1. By controlling the DC voltage intensity of GAIN, the DC current intensity of NODE1 is controlled, and the DC current intensity of the Q3 constant current source distributed to Q10 is controlled, so that the AC current intensity on the collector of Q10B and the collector of Q10A is determined, thereby realizing the control of the gain.

[0046] The structure of the differential voltage amplification module is shown in Figure 3 The differential voltage output by the input stage amplification module is input to the current stage circuit through ports S1- and S1+. The current stage circuit outputs the input differential voltage after gain or attenuation. Figure 3 V1 is a packaged pair of switching diodes, and D1 is a single switching diode. V1 and D1 form a DC voltage clamping circuit for the differential output of the current stage amplifier. Resistors R1, R2, R3 and R4 are the collector resistors of transistor Q1. Q1 (Q1A and Q1B) is a packaged pair of NPN small-signal transistors, which form a differential input pair of the differential amplifier. Transistor Q2, resistor R8 and R9 form a constant current source of the differential amplification circuit of the current stage amplifier, which has the function of controlling the voltage of the GAIN interface to control the gain of the current stage.

[0047] According to the order of Figure 1 , Figure 2 , Figure 3 , the circuit is cascaded, that is, the bias and gain adjustable current amplifier provided in the embodiment has the working principle as follows:

[0048] The differential voltage and the direct current bias are input into the present circuit through ports S1- and S1+, S1- is input into the base of Q1A 1, S1+ is input into the base of Q1B 2, the current intensity of the collector of Q1A 6 meets a fixed positive proportion with the voltage intensity of the base of Q1A 1, the phases are same, the amplified voltage signal of the collector of Q1A 6 which is opposite to the voltage of the base of Q1A 1 is output through R1, and the voltage signal is output into S2- through V1 D1 direct current level clamping circuit. The base of Q1B 2 and the collector of Q1B 3 are same, the amplified voltage signal of the collector of Q1B 3 which is opposite to the base of Q1B 2 is output through V1 D1 direct current level clamping circuit, and the voltage signal is output into S2+. S2- and S2+ meet the differential relation, R3 and R4 are used as current limiting resistors to avoid the direct current of the collector of Q1A 6 and the collector of Q1B 3 being too large due to the change of the direct current bias.

[0049] Suppose that there is a common mode voltage signal on ports S1+ and S1-, because of the constant current characteristics of Q2, R8 and R9, the current intensity of the collector of Q1B 3 is same with the collector of Q1A 6, and the current phases are opposite, and the voltage signal intensity of the collector of Q1B 3 is same with the collector of Q1A 6, and the voltage phases are opposite, so the common mode voltage signal input from ports S1+ and S1- is strengthened and suppressed.

[0050] The gain adjustment direct current voltage signal is input from port GAIN, and is input into the base of Q2 1 through R8. R8, Q2 and R9 constitute a voltage controlled constant current source, the gain adjustment direct current voltage signal is in positive proportion with the output current intensity of the collector of Q2 3, and the output current intensity of the collector of Q2 3 is adjusted by adjusting the intensity of the gain adjustment direct current voltage signal. The collector of Q2 3 and the emitter of Q1A 5 and the emitter of Q1B 4 are connected to the same node NODE2, so as to control the direct current intensity of NODE2. The gain of the differential voltage amplification module is determined by the direct current intensity of P2 node, so the gain of the differential voltage amplification module can be controlled by adjusting the direct current intensity input into port GAIN.

[0051] Embodiment 2: amplification of current signal of photomultiplier tube

[0052] In this embodiment, the current amplifier described in embodiment 1 is used to amplify the current signal of the photomultiplier tube.

[0053] The photomultiplier tube (PMT) is commonly used as a front-end detection sensor in weak light detection and sensing, and the output signal characteristics are as follows:

[0054] (1) current signal output;

[0055] (2) the output intensity of the current signal is positively correlated with the input light intensity;

[0056] (3) When the input light is continuous light, pulsed light, single photon, etc., the output of the PMT is a current pulse signal, and the time and phase characteristics of the input light signal can be preserved;

[0057] (4) The intensity range of the current pulse output is about 10uApeak~160uApeak.

[0058] This embodiment takes the PMT as a front-end detection sensor device, and inputs the "current amplifier" IN signal input interface respectively:

[0059] (a) 10uApeak 5ns pulse width, 200ns continuous pulse signal.

[0060] (b) 160uApeak 5ns pulse width, 200ns continuous pulse signal.

[0061] S2+ and S2- are voltage signal output interfaces, BIAS input is grounded, and GAIN input is a direct current level of -5.8V.

[0062] When observing the time domain waveform at the output interface S2+ and S2-, the waveform diagram shown in Figure 4 , Figure 5 is obtained, the blue waveform is the output signal, and the orange waveform is the input signal. It can be observed that the "current amplifier" responds to the above pulse: the input current signal is amplified, the phase is delayed, the phase relationship between the pulses is preserved, there is no obvious overshoot and back cavity, and the signal is effectively amplified.

[0063] In order to highlight the amplification effect of the current amplifier, this embodiment compares the performance of the integrated operational amplifier under the same input and output conditions:

[0064] An operational amplifier AD-845 with similar parameters to the current amplifier in this embodiment is selected, and the AD-845 is connected to the ground through a resistor with the same resistance value as R23 in the current amplifier in this embodiment. The operational amplifier is connected in the form of a follower without external compensation circuit, and the supply voltage is ±12V. The input signal is consistent with the above condition (b).

[0065] When observing the voltage output waveform at the output end of the integrated operational amplifier, the waveform diagram shown in Figure 6 .

[0066] As shown in Figure 6 , the blue waveform is the output signal, and the orange waveform is the input signal. It can be observed that the integrated operational amplifier responds to the above pulse: the input current signal is amplified, the phase is delayed, the phase relationship between the pulse peaks is preserved, the overshoot and back cavity amplitude is too large, and the signal is not effectively amplified.

[0067] Therefore, the current amplifier provided in this embodiment can achieve better amplification effect compared to the integrated operational amplifier.

[0068] Example 3:

[0069] This embodiment verifies through simulation whether the current amplifier described in Embodiment 1 has adjustable gain.

[0070] Similarly, ports S2+ and S2- are voltage signal output interfaces.

[0071] BIAS input is grounded; GAIN inputs are -6.8V, -6.3V, -5.8V, -5.3V and -4.8V DC levels respectively; IN interface input signal source is AC scanning signal source, set current signal amplitude to 100uA.

[0072] The gain-frequency curves of the current amplifier are as follows: Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 As shown, GAIN_in is the DC level value of the input GAIN interface. GAIN is the gain value, dimensionless, expressed in dB. Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 The value of the middle gain flattening stage is obtained as follows Figure 12 The curve in the middle, from Figure 12 It can be seen that as the absolute value of the DC level at the GAIN interface increases, the gain value decreases, meaning that the current amplifier in this embodiment can achieve adjustable gain.

[0073] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A current amplifier, characterized by, The input stage amplification module comprises: a triode Q10A, a triode Q10B, a switching diode V2A, a switching diode V2B, a Zener diode V3, a direct current zeroing resistor network, a first constant current source, a constant current circuit with a current buffer; the triode Q10A and the triode Q10B are a pair of PNP small-signal triodes in a package, and constitute a differential input pair of a differential amplifier; the base of the triode Q10A is grounded, the emitter is connected to the first constant current source through a resistor R21, and the collector is connected to the anode of the switching diode V2A; the base of the triode Q10B is connected to a current input end, the emitter is connected to the direct current zeroing resistor network, and the collector is connected to the anode of the switching diode V2B; the switching diode V2A, the switching diode V2B and the Zener diode V3 constitute a direct current clamping circuit at an output end; the constant current circuit with the current buffer comprises a resistor R29, a resistor R30, a resistor R38, a triode Q7 and a triode Q11, a gain control voltage input port is connected to the base of the triode Q11 through the resistor R29 and the resistor R30, and one end connected by the resistor R29 and the resistor R30 is grounded through a capacitor C6; the emitter of the triode Q11 is grounded, and the collector is connected to the emitter of the triode Q7; the base of the triode Q7 is grounded, and the collector is connected to the first constant current source. The differential voltage amplification module comprises: a switching diode pair V1, a switching diode D1, a pair of NPN small-signal triodes Q1A and Q1B, and a second constant current source; the switching diode pair V1 and the switching diode D1 constitute a direct current voltage clamping circuit for differential output of the input stage amplifier; the differential alternating voltage is input through two bases of the pair of NPN small-signal triodes Q1A and Q1B; two emitters of the pair of NPN small-signal triodes Q1A and Q1B are connected to the second constant current source, two collectors are respectively connected to a power supply through a resistor R1, a resistor R3, a resistor R2 and a resistor R4, and the output differential voltage is output from one end connected by the resistor R1 and the resistor R3 and one end connected by the resistor R2 and the resistor R4. The direct current zeroing resistor network comprises: a resistor R15, a resistor R22 and a resistor R18; the resistor R15 and the resistor R18 are connected in parallel and then connected in series with the resistor R22, one end connected by the resistor R15 and the resistor R18 is connected to one end connected by the second constant current source and the constant current circuit with the current buffer, and the other end of the resistor R22 not connected to the resistor R18 and the resistor R15 is connected to the emitter of the triode Q10B.

2. The current amplifier of claim 1, wherein, ​ 3. The current amplifier of claim 1, wherein, The first constant current source comprises: resistors R10, R11, R14 and a transistor Q3; the emitter of the transistor Q3 is connected to a power supply through the resistor R10, the collector is connected to the constant current circuit of the current buffer, the emitter resistor of the transistor Q10A and the DC zeroing resistor network of the transistor Q10B, and the base is connected to one end of the resistor R11 and the resistor R14.

4. The current amplifier of claim 1, wherein, The second constant current source comprises: a transistor Q2, a resistor R8 and a resistor R9; the base of the transistor Q2 is connected to a gain control voltage input terminal GAIN, the emitter is connected to a -9V power supply through the resistor R9, and the collector is connected to the emitter of the NPN small signal transistor pair Q1A and Q1B.

5. The current amplifier of claim 1, wherein, The cathodes of the switching diodes V2A and V2B are respectively connected to a resistor R42 and the anode of a Zener diode V3, the other end of the resistor R42 is connected to a -9V power supply, and the cathode of the Zener diode V3 is grounded.

6. The current amplifier of claim 1, wherein, The two anodes of the switching diode pair V1 are respectively connected to one end of the resistor R1 and the resistor R3, one end of the resistor R2 and the resistor R4, the cathode is connected to the anode of the switching diode D1, and the cathode of the switching diode D1 is grounded.

7. The current amplifier of claim 1, wherein, The DC bias conversion module comprises resistors R5, R6, R7, capacitors C1 and C2; the resistors R5, R6 and R7 are connected in sequence; the input end of the resistor R5 is connected to an amplifier DC voltage bias input interface, and the output end of the resistor R7 is connected to a current input end IN; one end of the capacitor C1 is connected to one end of the resistors R5 and R6, and the other end is grounded; one end of the capacitor C2 is connected to one end of the resistors R6 and R7, and the other end is grounded.

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