Ultralow-noise hydrophone amplification circuit

By using differential amplification module, voltage follow circuit and negative feedback module in the hydrophone amplification circuit, adjusting the source-level current of the high-pass filter and field effect tube, the problem of difficulty in reducing voltage and current noise in the prior art is solved. It realizes efficient noise optimization in low-noise measurement environment.

CN119135095APending Publication Date: 2024-12-13CHANGSHA LANSHENG TECH CO LTD
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Patent Information

Application Number
CN202311577294.X
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2023-11-24
Publication Date
2024-12-13

AI Technical Summary

Technical Problem

Existing integrated operational amplifiers are difficult to reduce voltage and current noise at the same time in low-noise measurement environments, and cannot meet the low-noise demand of hydrophones.

Method used

The differential amplification module, voltage follow circuit module and negative feedback module are used to optimize the input noise of the entire circuit by adjusting the high-pass filter cutoff frequency and the source-level current of the field effect tube. The specific implementation includes a differential amplification module connecting the voltage following circuit module and the negative feedback module, and a high-pass filter is formed using capacitors and resistors to adjust the static bias voltage to affect the working current of the field effect tube, thereby optimizing noise.

Benefits of technology

It realizes the reduction of input noise in a low-noise measurement environment, meets the needs of ultra-low noise hydrophone amplifier circuits, and maintains wide signal bandwidth and low input noise under a single power supply state.

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Abstract

The invention relates to the technical field of electronic circuits, in particular to an ultra-low noise hydrophone amplifying circuit. The ultra-low noise hydrophone amplification circuit comprises a differential amplification circuit module, a voltage follower circuit module and a negative feedback module. In the differential amplification module, a sixth capacitor C6 and an eighth resistor R8 are used to form a first-order high-pass filter, and the high-pass cut-off frequency is adjusted and the input noise is reduced by adjusting the values of the sixth capacitor C6 and the eighth resistor R8, so that the requirement of the amplification circuit for the environment needing low-noise measurement is met; the eighth resistor R8 provides a 0V static bias voltage for the grid electrode of the first field effect transistor Q1, and the working current of the field effect transistor can be changed by adjusting the static bias voltage, so that the thermal noise related to the resistor is further influenced, and the input noise can be optimized by adjusting the resistance value of the eighth resistor R8.
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Description

Technical Field

[0001] The present application relates to the technical field of electronic circuits, and in particular to an ultra-low noise hydrophone amplifier circuit. Background Art

[0002] In the field of underwater acoustics, a hydrophone is a sensor that converts underwater acoustic signals into electrical signals. It plays an important role in target identification, underwater acoustic communications, topographic mapping, noise measurement and other fields. The commonly used piezoelectric ceramic type hydrophone has a high output impedance, so it is necessary to use an amplifier with high input impedance to match and amplify the hydrophone signal. At the same time, the amplifier adapted to the hydrophone must simultaneously keep the voltage noise and current noise very low to meet the application requirements of the low-noise measurement environment. Although the existing integrated operational amplifier can solve the impedance matching problem, it is difficult to keep the voltage noise and current noise at the input of the integrated operational amplifier very low at the same time, which makes it difficult to apply to environments that require low-noise measurements. Summary of the invention

[0003] In response to the above problems, the present application adjusts the cutoff frequency of the high-pass filter and the source current of the field effect transistor through interconnected differential amplifier modules, voltage follower circuit modules and negative feedback modules, thereby changing the input noise of the entire circuit.

[0004] The technical solution of the present application is: the ultra-low noise hydrophone amplifier circuit includes a differential amplifier module, a voltage follower circuit module and a negative feedback module;

[0005] The differential amplifier module is connected to the voltage follower circuit module and the negative feedback module to obtain the input signal of the hydrophone and is used to amplify the voltage of the input signal;

[0006] The voltage follower circuit module is connected to the differential amplifier module and the negative feedback module, stabilizes the output voltage of the differential amplifier module, further amplifies the voltage of the input signal, and outputs the signal;

[0007] The negative feedback module is connected to the differential amplifier module and the voltage follower circuit module, and adjusts the output voltage of the differential amplifier module according to the output voltage of the voltage follower circuit module.

[0008] As a further preferred solution, the differential amplifier module includes a third capacitor C3, a sixth capacitor C6, a third resistor R3, a fourth resistor R4, an eighth resistor R8, a ninth resistor R9, an access voltage VCC, a first field effect transistor Q1 and a second field effect transistor Q2;

[0009] The gate of the first field effect transistor Q1 is connected to one end of the hydrophone through the sixth capacitor C6, and the other end of the hydrophone is grounded. One end of the ninth resistor R9 is respectively connected to the source of the first field effect transistor Q1 and the source of the second field effect transistor Q2, and the other end of the ninth resistor R9 is grounded. The access voltage VCC is connected to the drain of the first field effect transistor Q1 through the third resistor R3, and is connected to the drain of the second field effect transistor Q2 through the fourth resistor R4. The drain of the first field effect transistor Q1 and one end of the sixth capacitor C6 are grounded through the eighth resistor R8. The drain of the second field effect transistor Q2 is connected to the negative feedback module. One end of the third capacitor C3 is respectively connected to the drain of the first field effect transistor Q1 and one end of the third resistor, and the other end is respectively connected to one end of the fourth resistor R4 and the drain of the second field effect transistor Q2, and both ends of the third capacitor C3 are connected to the voltage follower circuit module.

[0010] As a further preferred solution, the voltage follower circuit module includes a first capacitor C1, a second capacitor C2, a fourth capacitor C4, a fifth capacitor C5, a first resistor R1, a second resistor R2, a fifth resistor R5, a sixth resistor R6, a twelfth resistor R12 and a first operational amplifier U1;

[0011] The power supply terminal of the first operational amplifier U1 is connected to the access voltage VCC, the ground terminal is grounded, the input terminal is respectively connected to one end of the second capacitor C2 and one end of the fifth resistor R5, the other end of the second capacitor C2 is respectively connected to one end of the fourth resistor R4 and the drain of the second field effect transistor Q2, one end of the first resistor R1, one end of the second resistor R2, and one end of the first capacitor C1 are respectively connected to the other end of the fifth resistor R5, the other end of the first resistor R1 and the other end of the first capacitor C1 are both grounded, and the other end of the second resistor R2 is respectively connected to the access voltage VCC and the power supply terminal of the first operational amplifier U1;

[0012] The inverting input terminal of the first operational amplifier U1 is respectively connected to one end of the fourth capacitor C4 and one end of the sixth resistor R6, the other end of the fourth capacitor C4 is respectively connected to the drain of the first field effect transistor Q1 and one end of the third resistor R3, and the other end of the sixth resistor R6 is connected to the output terminal of the first operational amplifier U1;

[0013] The output end of the first operational amplifier U1 is connected to one end of the fifth capacitor, the other end of the fifth capacitor is connected to one end of the twelfth resistor R12, and the other end of the twelfth resistor R12 is grounded.

[0014] As a further preferred solution, the negative feedback module includes a seventh capacitor C7, an eighth capacitor C8, a seventh resistor R7, a tenth resistor R10 and an eleventh resistor R11;

[0015] The gate of the second field effect transistor Q2 is respectively connected to one end of the seventh capacitor C7 and one end of the tenth resistor R10, the other end of the seventh capacitor C7 is respectively connected to one end of the seventh resistor R7, one end of the eighth capacitor C8, and one end of the eleventh resistor R11, the other end of the seventh resistor R7 and the other end of the eighth capacitor C8 are respectively connected to the output end of the first operational amplifier U1, and the other end of the tenth resistor R10 and the other end of the eleventh resistor R11 are grounded;

[0016] As a further preferred solution, the first field effect transistor Q1 and the second field effect transistor Q2 are a pair of matched junction field effect transistors, and the ninth resistor R9 can enable the source of the first field effect transistor Q1 and the source of the second field effect transistor Q2 to obtain a suitable static bias voltage.

[0017] As a further preferred solution, the second capacitor C2 and the fifth resistor R5 form a first-order high-pass filter, and the second capacitor C2 can be used to adjust the DC voltage between the in-phase terminal of the first operational amplifier U1 and the drain of the second field effect transistor Q2. The second capacitor C2 is an adjustable capacitor, and the fifth resistor R5 is an adjustable resistor.

[0018] As a further preferred solution, the sixth capacitor C6 and the eighth resistor R8 form a first-order high-pass filter, and the sixth capacitor C6 is an adjustable capacitor, and the eighth resistor R8 is an adjustable resistor.

[0019] As a further preferred solution, the fourth capacitor C4 can isolate the DC voltage between the inverting terminal of the first operational amplifier U1 and the drain of the first field effect transistor Q1, and the fourth capacitor C4 is an adjustable capacitor, and the sixth resistor R6 is an adjustable resistor.

[0020] This application has the following advantages:

[0021] 1. The present invention uses the sixth capacitor C6 and the eighth resistor R8 to form a first-order high-pass filter in the differential amplifier module, and adjusts the high-pass cutoff frequency and reduces the input noise by adjusting the values ​​of the sixth capacitor C6 and the eighth resistor R8, so as to meet the requirements of the amplifier circuit for an environment requiring low-noise measurement. The eighth resistor R8 provides a 0V static bias voltage for the gate of the first field effect transistor Q1. Since the working current of the field effect transistor can be changed by adjusting the static bias voltage, thereby affecting the thermal noise related to the resistor, adjusting the resistance value of the eighth resistor R8 can also optimize the input noise.

[0022] 2. In the present invention, in the voltage follower circuit module, the second capacitor C2 and the fifth resistor R5, the fourth capacitor C4 and the sixth resistor R6 respectively form a first-order high-pass filter, and the second capacitor C2 can isolate the DC voltage between the in-phase terminal of the first operational amplifier U1 and the drain of the second field effect transistor Q2.

[0023] 3. The present invention uses a negative feedback module, and the fifth capacitor C5 and the eighth resistor R8, the seventh capacitor C7 and the tenth resistor R10 respectively form a first-order high-pass filter together, and the eighth capacitor C8 and the seventh resistor R7 form a low-pass filter together to reduce the gain of the out-of-band high-frequency signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0025] Figure 1 Schematic diagram of the structure of the ultra-low noise hydrophone amplifier circuit provided in the embodiment of the present application.

[0026] Figure 2 This is a circuit structure block diagram of an ultra-low noise hydrophone amplifier circuit provided in an embodiment of the present application.

[0027] Figure 3 This is a gain performance effect diagram of the ultra-low noise hydrophone amplifier circuit provided in the embodiment of the present application.

[0028] Figure 4 This is a noise reduction performance effect diagram of the ultra-low noise hydrophone amplifier circuit provided in the embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application clearer, some embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and Examples. 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. However, it will be appreciated by those skilled in the art that in the various embodiments of the present application, many technical details are proposed in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present application can also be implemented.

[0030] Example 1

[0031] Ultra-low noise hydrophone amplifier circuit, such as Figure 1 As shown, it is divided into three modules, including a differential amplifier circuit module, a voltage follower circuit module and a negative feedback module. The connection relationship is as follows Figure 2 As shown;

[0032] The differential amplifier module is connected to the voltage follower circuit module and the negative feedback module to obtain the input signal of the hydrophone and is used to amplify the voltage of the input signal;

[0033] The voltage follower circuit module is connected to the differential amplifier module and the negative feedback module, stabilizes the output voltage of the differential amplifier module, further amplifies the voltage of the input signal, and outputs the signal;

[0034] The negative feedback module is connected to the differential amplifier module and the voltage follower circuit module, and adjusts the output voltage of the differential amplifier module according to the output voltage of the voltage follower circuit module.

[0035] like Figure 1 and Figure 2 As shown, the differential amplifier module includes a third capacitor C3, a sixth capacitor C6, a third resistor R3, a fourth resistor R4, an eighth resistor R8, a ninth resistor R9, an access voltage VCC, a first field effect transistor Q1 and a second field effect transistor Q2, wherein the first field effect transistor Q1 and the second field effect transistor Q2 are both IF9030 field effect transistors;

[0036] In this embodiment, the value of the third capacitor C3 is set to 1nF, the value of the sixth capacitor C6 is set to 1uF, the value of the third resistor R3 is set to 400Ω, the value of the fourth resistor R4 is set to 400Ω, the value of the eighth resistor R8 is set to 10MΩ, and the value of the ninth resistor R9 is set to 150Ω.

[0037] The gate of the first field effect transistor Q1 is connected to one end of the hydrophone through the sixth capacitor C6, and the other end of the hydrophone is grounded. One end of the ninth resistor R9 is respectively connected to the source of the first field effect transistor Q1 and the source of the second field effect transistor Q2, and the other end of the ninth resistor R9 is grounded. The access voltage VCC is connected to the drain of the first field effect transistor Q1 through the third resistor R3, and is connected to the drain of the second field effect transistor Q2 through the fourth resistor R4. The drain of the first field effect transistor Q1 and one end of the sixth capacitor C6 are grounded through the eighth resistor R8, and the drain of the second field effect transistor Q2 is connected to the negative feedback module. One end of the third capacitor C3 is respectively connected to the drain of the first field effect transistor Q1 and one end of the third resistor, and the other end is respectively connected to one end of the fourth resistor R4 and the drain of the second field effect transistor Q2, and both ends of the third capacitor C3 are connected to the voltage follower circuit module. The third capacitor C3 can improve the gain of the high frequency band of the circuit, thereby expanding the bandwidth of the high frequency band of the circuit.

[0038] like Figure 1As shown, the first field effect transistor Q1 and the second field effect transistor Q2 are a pair of well-matched junction field effect transistors, and the ninth resistor R9 can enable the source of the first field effect transistor Q1 and the source of the second field effect transistor Q2 to obtain a suitable static bias voltage, so that the first field effect transistor Q1 and the second field effect transistor Q2 work in the linear amplification region. By adjusting the resistance value of the ninth resistor R9, the source current of the first field effect transistor Q1 and the second field effect transistor Q2 can be adjusted, thereby changing the input noise of the entire circuit. Since the amplifier may have a lower noise level at a low source current and may have a higher noise level at a high source current, by adjusting the resistance value of the resistor related to the source current of the field effect transistor in the circuit, the operating point of the circuit can be changed, thereby affecting the gain, linearity and input noise of the amplifier, thereby changing the input noise of the entire circuit.

[0039] It should be specially supplemented that the sixth capacitor C6 is a variable capacitor, the eighth resistor R8 is a variable resistor, the hydrophone is connected to the circuit through one end of the sixth capacitor C6, and the other end of the sixth capacitor C6 and the eighth resistor R8 form a first-order high-pass filter. Since a lower cut-off frequency allows more low-frequency noise to pass through the filter, and a higher cut-off frequency reduces the transmission of low-frequency noise, the input noise can be reduced by changing the cut-off frequency of the high-pass filter. Therefore, by changing the values ​​of the sixth capacitor C6 and the eighth resistor R8, the high-pass cut-off frequency can be adjusted, thereby changing the size of the noise. At the same time, the eighth resistor R8 provides a static bias voltage of 0V for the gate of the first field effect transistor Q1. Since the working current can be adjusted by adjusting the static bias voltage, thereby affecting the thermal noise related to the resistor, adjusting the resistance value of the eighth resistor R8 can also optimize the noise of the device.

[0040] The third resistor R3 and the fourth resistor R4 select appropriate values ​​according to the size of the access voltage VCC to provide a reasonable bias voltage to the drain of the first field effect transistor Q1 and the second field effect transistor Q2.

[0041] The present invention uses a sixth capacitor C6 and an eighth resistor R8 to form a first-order high-pass filter in a differential amplifier module, and adjusts the high-pass cutoff frequency and reduces input noise by adjusting the values ​​of the sixth capacitor C6 and the eighth resistor R8, so as to meet the requirements of the amplifier circuit for an environment requiring low-noise measurement. The eighth resistor R8 provides a 0V static bias voltage for the gate of the first field effect transistor Q1. Since the static bias voltage can be adjusted to reduce the operating current, thereby affecting the thermal noise related to the resistor, adjusting the resistance value of the eighth resistor R8 can also optimize the input noise.

[0042] like Figure 1 and Figure 2As shown, the voltage follower circuit module includes a first capacitor C1, a second capacitor C2, a fourth capacitor C4, a fifth capacitor C5, a first resistor R1, a second resistor R2, a fifth resistor R5, a sixth resistor R6, a twelfth resistor R12 and a first operational amplifier U1, wherein the first operational amplifier U1 adopts an ADA4807-1 single-channel operational amplifier;

[0043] In this embodiment, the value of the first capacitor C1 is set to 22uF, the value of the second capacitor C2 is set to 22uF, the value of the fourth capacitor C4 is set to 22uF, the value of the fifth capacitor C5 is set to 22uF, the value of the first resistor R1 is set to 10kΩ, the value of the second resistor R2 is set to 10kΩ, the value of the fifth resistor R5 is set to 100kΩ, the value of the sixth resistor R6 is set to 100kΩ, and the value of the twelfth resistor R12 is set to 100kΩ.

[0044] The power supply end of the first operational amplifier U1 is connected to the access voltage VCC, the ground end is grounded, the input end is respectively connected to one end of the second capacitor C2 and one end of the fifth resistor R5, the other end of the second capacitor C2 is respectively connected to one end of the fourth resistor R4 and the drain of the second field effect transistor Q2, one end of the first resistor R1, one end of the second resistor R2, and one end of the first capacitor C1 are respectively connected to the other end of the fifth resistor R5, the other end of the first resistor R1 and the other end of the first capacitor C1 are both grounded, and the other end of the second resistor R2 is respectively connected to the access voltage VCC and the power supply end of the first operational amplifier U1. The first resistor R1 and the second resistor R2 form a voltage divider network, and a voltage is obtained by the access voltage VCC to provide a bias voltage for the in-phase end of the first operational amplifier U1. The first capacitor C1, the first resistor R1, and the second resistor R2 together form a low-pass filter to reduce the noise brought to the in-phase end of the first operational amplifier U1 by the access power access voltage VCC;

[0045] The inverting input terminal of the first operational amplifier U1 is respectively connected to one end of the fourth capacitor C4 and one end of the sixth resistor R6, the other end of the fourth capacitor C4 is respectively connected to the drain of the first field effect transistor Q1 and one end of the third resistor R3, and the other end of the sixth resistor R6 is connected to the output terminal of the first operational amplifier U1;

[0046] The output end of the first operational amplifier U1 is connected to one end of the fifth capacitor, the other end of the fifth capacitor is connected to one end of the twelfth resistor R12, and the other end of the twelfth resistor R12 is grounded.

[0047] It should be particularly supplemented that the second capacitor C2 is an adjustable capacitor, the fifth resistor R5 is an adjustable resistor, the second capacitor C2 and the fifth resistor R5 form a first-order high-pass filter, and the second capacitor C2 can isolate the DC voltage between the in-phase terminal of the first operational amplifier U1 and the drain of the second field effect transistor Q2.

[0048] The fourth capacitor C4 is an adjustable capacitor, and the sixth resistor R6 is an adjustable resistor. The fourth capacitor C4 can isolate the DC voltage between the inverting end of the first operational amplifier U1 and the drain of the first field effect transistor Q1. The fourth capacitor C4 and the sixth resistor R6 form a first-order high-pass filter. By adjusting the value of the fourth capacitor C4 or the sixth resistor R6, the cutoff frequency of the high-pass filter can be changed.

[0049] like Figure 1 and Figure 2 As shown, the negative feedback module includes a seventh capacitor C7, an eighth capacitor C8, a seventh resistor R7, a tenth resistor R10 and an eleventh resistor R11. In this embodiment, the value of the seventh capacitor C7 is set to 22uF, the value of the eighth capacitor C8 is set to 150pF, the value of the seventh resistor R7 is set to 5kΩ, the value of the tenth resistor R10 is set to 10MΩ, and the value of the eleventh resistor R11 is set to 50Ω;

[0050] The gate of the second field effect transistor Q2 is respectively connected to one end of the seventh capacitor C7 and one end of the tenth resistor R10, the other end of the seventh capacitor C7 is respectively connected to one end of the seventh resistor R7, one end of the eighth capacitor C8, and one end of the eleventh resistor R11, the other end of the seventh resistor R7 and the other end of the eighth capacitor C8 are respectively connected to the output end of the first operational amplifier U1, and the other end of the tenth resistor R10 and the other end of the eleventh resistor R11 are grounded;

[0051] It should be particularly supplemented that the seventh resistor R7 and the eleventh resistor R11 are variable resistors. By adjusting the value of the seventh resistor R7 or the eleventh resistor R11, the gain of the entire amplifier circuit can be adjusted, and the eighth capacitor C8 and the seventh resistor R7 together form a low-pass filter to reduce the gain of out-of-band high-frequency signals.

[0052] The seventh capacitor C7 and the tenth resistor R10 together form a first-order high-pass filter, which can isolate the DC voltage from the negative feedback network. At the same time, the tenth resistor R10 provides a static bias voltage of 0V for the gate of the second field effect transistor Q2.

[0053] The fifth capacitor C5 and the eighth resistor R8 together form a first-order high-pass filter, which can isolate the DC voltage from the output end of the first operational amplifier U1.

[0054] Example 2

[0055] The performance of the ultra-low noise hydrophone amplifier circuit is simulated, and the results are as follows: Figure 3 and Figure 4As shown, from the results, the maximum gain is about 39.5dB, and the -3dB bandwidth is 1Hz-400KHz. The equivalent input noise voltage spectral density is basically stable at 1.6nV / √Hz within 10Hz-100KHz, which is in line with the design expectations. In order to verify the actual performance of the low-noise amplifier circuit, the corresponding physical PCB board was processed, with an area of ​​only 7mm×15mm. Then its actual performance was tested: the present invention uses a DC power supply to provide the circuit with a working voltage, and then uses a signal generator to provide a sinusoidal AC signal with a peak value of 10mV at the input end of the circuit, and uses an oscilloscope to read the circuit output amplitude.

[0056] According to the measured results, the actual maximum gain reaches 40dB, and the -3dB bandwidth is about 1Hz-412KHz. Taking into account the precision error of components, the result is basically consistent with the expected value and meets the design requirements.

[0057] In summary, the present invention utilizes an ultra-low noise field effect transistor as the front stage of the amplifier circuit for impedance matching and preliminary amplification, utilizes an operational amplifier as the output stage to improve the load capacity, utilizes a feedback network to stabilize the circuit working state, and utilizes capacitors to isolate the DC bias voltages of each stage, so that the entire circuit can maintain ultra-low input noise and a wider signal bandwidth even under a single power supply state.

[0058] It should be understood that those skilled in the art can follow the above-described process and all the obtained results fall within the scope of protection of the claims attached to this application. Parts not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. Ultra-low noise hydrophone amplifier circuit, characterized in that, It includes a differential amplifier module, a voltage follower circuit module and a negative feedback module; The differential amplifier module is connected to the voltage follower circuit module and the negative feedback module to obtain the input signal of the hydrophone and is used to amplify the voltage of the input signal; The voltage follower circuit module is connected to the differential amplifier module and the negative feedback module, stabilizes the output voltage of the differential amplifier module, further amplifies the voltage of the input signal, and outputs the signal; The negative feedback module is connected to the differential amplifier module and the voltage follower circuit module, and adjusts the output voltage of the differential amplifier module according to the output voltage of the voltage follower circuit module.

2. The ultra-low noise hydrophone amplifier circuit according to claim 1, characterized in that: The differential amplifier module includes a third capacitor C3, a sixth capacitor C6, a third resistor R3, a fourth resistor R4, an eighth resistor R8, a ninth resistor R9, an access voltage VCC, a first field effect transistor Q1 and a second field effect transistor Q2; The gate of the first field effect transistor Q1 is connected to one end of the hydrophone through the sixth capacitor C6, and the other end of the hydrophone is grounded. One end of the ninth resistor R9 is respectively connected to the source of the first field effect transistor Q1 and the source of the second field effect transistor Q2, and the other end of the ninth resistor R9 is grounded. The access voltage VCC is connected to the drain of the first field effect transistor Q1 through the third resistor R3, and is connected to the drain of the second field effect transistor Q2 through the fourth resistor R4. The drain of the first field effect transistor Q1 and one end of the sixth capacitor C6 are grounded through the eighth resistor R8. The drain of the second field effect transistor Q2 is connected to the negative feedback module. One end of the third capacitor C3 is respectively connected to the drain of the first field effect transistor Q1 and one end of the third resistor, and the other end is respectively connected to one end of the fourth resistor R4 and the drain of the second field effect transistor Q2, and both ends of the third capacitor C3 are connected to the voltage follower circuit module.

3. The ultra-low noise hydrophone amplifier circuit according to claim 2, characterized in that: The voltage follower circuit module includes a first capacitor C1, a second capacitor C2, a fourth capacitor C4, a fifth capacitor C5, a first resistor R1, a second resistor R2, a fifth resistor R5, a sixth resistor R6, a twelfth resistor R12 and a first operational amplifier U1; The power supply terminal of the first operational amplifier U1 is connected to the access voltage VCC, the ground terminal is grounded, the input terminal is respectively connected to one end of the second capacitor C2 and one end of the fifth resistor R5, the other end of the second capacitor C2 is respectively connected to one end of the fourth resistor R4 and the drain of the second field effect transistor Q2, one end of the first resistor R1, one end of the second resistor R2, and one end of the first capacitor C1 are respectively connected to the other end of the fifth resistor R5, the other end of the first resistor R1 and the other end of the first capacitor C1 are both grounded, and the other end of the second resistor R2 is respectively connected to the access voltage VCC and the power supply terminal of the first operational amplifier U1; The inverting input terminal of the first operational amplifier U1 is respectively connected to one end of the fourth capacitor C4 and one end of the sixth resistor R6, the other end of the fourth capacitor C4 is respectively connected to the drain of the first field effect transistor Q1 and one end of the third resistor R3, and the other end of the sixth resistor R6 is connected to the output terminal of the first operational amplifier U1; The output end of the first operational amplifier U1 is connected to one end of the fifth capacitor, the other end of the fifth capacitor is connected to one end of the twelfth resistor R12, and the other end of the twelfth resistor R12 is grounded.

4. The ultra-low noise hydrophone amplifier circuit according to claim 3, characterized in that: The negative feedback module includes a seventh capacitor C7, an eighth capacitor C8, a seventh resistor R7, a tenth resistor R10 and an eleventh resistor R11: The gate of the second field effect transistor Q2 is respectively connected to one end of the seventh capacitor C7 and one end of the tenth resistor R10, the other end of the seventh capacitor C7 is respectively connected to one end of the seventh resistor R7, one end of the eighth capacitor C8, and one end of the eleventh resistor R11, the other end of the seventh resistor R7 and the other end of the eighth capacitor C8 are respectively connected to the output end of the first operational amplifier U1, and the other end of the tenth resistor R10 and the other end of the eleventh resistor R11 are grounded.

5. The ultra-low noise hydrophone amplifier circuit according to claim 4, characterized in that: The first field effect transistor Q1 and the second field effect transistor Q2 are a pair of matched junction field effect transistors, and the ninth resistor R9 is used to obtain a suitable static bias voltage for the source of the first field effect transistor Q1 and the source of the second field effect transistor Q2.

6. The ultra-low noise hydrophone amplifier circuit according to claim 5, characterized in that: The second capacitor C2 and the fifth resistor R5 form a first-order high-pass filter, and the second capacitor C2 can isolate the DC voltage between the in-phase terminal of the first operational amplifier U1 and the drain of the second field effect transistor Q2. The second capacitor C2 is an adjustable capacitor, and the fifth resistor R5 is an adjustable resistor.

7. The ultra-low noise hydrophone amplifier circuit according to claim 6, characterized in that: The sixth capacitor C6 and the eighth resistor R8 form a first-order high-pass filter, and the sixth capacitor C6 is an adjustable capacitor, and the eighth resistor R8 is an adjustable resistor.

8. The ultra-low noise hydrophone amplifier circuit according to claim 6, characterized in that: The fourth capacitor C4 can isolate the DC voltage between the inverting terminal of the first operational amplifier U1 and the drain of the first field effect transistor Q1 , and the fourth capacitor C4 is an adjustable capacitor, and the sixth resistor R6 is an adjustable resistor.