gain circuit

Abstract

The application discloses a gain circuit, comprising: a first operational amplifier, a first feedback loop, a first end of the first feedback loop being connected with a reverse input end of the first operational amplifier, a second end of the first feedback loop being connected with an output end of the first operational amplifier, the first feedback loop and the first operational amplifier constituting a first gain circuit, the first gain circuit being used for providing a first gain for a first signal, a second feedback loop, the second feedback loop comprising a first diode unit, the first diode unit being connected in series between a first end and a second end of the second feedback loop, in the case that the first diode unit is turned on, the second feedback loop, the first feedback loop and the first operational amplifier constituting a second gain circuit, the second gain circuit being used for providing a second gain for the first signal. The circuit can adaptively adjust the gain, prevent signal saturation, and thus greatly widen the dynamic measurement range of the circuit.

Description

Technical Field

[0001] This application relates to the field of signal processing technology, and in particular to a gain circuit. Background Technology

[0002] With the rapid development of optoelectronic technology, in various applications related to optical sensors such as lidar, laser ranging, laser scanning, and laser communication, accurate measurement of the electrical signals converted from optical signals is crucial to ensure sensing accuracy.

[0003] In related technologies, an operational amplifier and a transimpedance circuit with a fixed gain are typically used to achieve photoelectric detection.

[0004] However, the range of signals that can be processed using related technologies is relatively limited, and the measurement results are not accurate enough when the signal varies greatly. Utility Model Content

[0005] Therefore, it is necessary to provide a gain circuit that can automatically switch the gain to adapt to different input signal variations, thus addressing the aforementioned technical problems.

[0006] This application provides a gain circuit, comprising: a first operational amplifier, the non-inverting input of which is connected to equivalent ground, and the inverting input of which is used to receive a first signal; a first feedback loop, the first end of which is connected to the inverting input of the first operational amplifier, and the second end of which is connected to the output of the first operational amplifier, wherein the first feedback loop and the first operational amplifier constitute a first gain circuit, which provides a first gain for the first signal; and a second feedback loop, the first end of which is connected to the inverting input of the first operational amplifier, and the second end of which is connected to the output of the first operational amplifier, wherein the second feedback loop includes a first diode unit connected in series between the first and second ends of the second feedback loop, wherein when the first diode unit is turned on, the second feedback loop, the first feedback loop, and the first operational amplifier constitute a second gain circuit, which provides a second gain for the first signal, and the first diode unit is turned on when the absolute value of the first signal is greater than a first threshold.

[0007] In one embodiment, the first feedback loop includes: a first resistor unit, a first end of which is connected to the inverting input terminal of the first operational amplifier, and a second end of which is connected to the output terminal of the first operational amplifier; the second feedback loop further includes: a second resistor unit, a first end of which is connected to the first end of the first diode unit, a second end of which is connected to the output terminal of the first operational amplifier, and a second end of the first diode unit is connected to the inverting input terminal of the first operational amplifier.

[0008] In one embodiment, the gain circuit further includes: a first voltage sampling module connected in parallel with a first diode unit, used to acquire a first voltage across the first diode unit and convert the first voltage into a second signal output; and a signal processing module connected to the output terminals of the first voltage sampling module and the first operational amplifier, used to subtract the second signal from the received third signal output by the first operational amplifier when the first diode unit is turned on, so as to obtain a second voltage across the second resistor unit, wherein the second voltage is used to indicate the parameters of the first signal.

[0009] In one embodiment, the gain circuit further includes a third feedback loop, which includes a third resistor unit and a second diode unit. The first end of the third resistor unit is connected to the first end of the second diode unit, the second end of the third resistor unit is connected to the output terminal of the first operational amplifier, and the second end of the second diode unit is connected to the inverting input terminal of the first operational amplifier. The second diode unit is used to conduct when the absolute value of the first signal is greater than a second threshold, and the second threshold is greater than the first threshold.

[0010] In one embodiment, the gain circuit further includes: a second voltage sampling module connected in parallel with the second diode unit, used to acquire a third voltage across the second diode unit and convert the third voltage into a fourth signal output; a signal processing module also connected to the second voltage sampling module, used to subtract the fourth signal from the received third signal output by the first operational amplifier when the second diode unit is turned on, so as to obtain a fourth voltage across the third resistor unit, wherein the fourth voltage is used to indicate the parameters of the first signal.

[0011] In one embodiment, the signal processing module includes: an analog-to-digital converter (ADC), which is connected to the output of a first voltage sampling module and a first operational amplifier and is connected to a reference voltage. The ADC is used to output a corresponding level signal based on the magnitude relationship between the second voltage and the reference voltage. A processor is connected to the output of the ADC. The processor is used to analyze the level signal to determine the target current value indicated by the first signal and to obtain the reflection parameter corresponding to the first signal based on the correspondence between the target current value and a preset current value and reflection parameters.

[0012] In one embodiment, the gain circuit further includes a filter circuit, which is connected in series between the output of the first operational amplifier and the signal processing module. The input of the filter circuit is connected to the output of the first operational amplifier, and the output of the filter circuit is connected to the input of the signal processing module. The filter circuit is used to filter out the DC component and the low-frequency component with a frequency lower than a preset cutoff frequency in the third signal output by the first operational amplifier.

[0013] In one embodiment, the filtering circuit includes: a first capacitor unit, a first end of which is connected to the output of a first operational amplifier, and a second end of which is connected to the input of a signal processing module; and a fourth resistor unit, a first end of which is connected to the second end of the first capacitor unit, and the second end of which is connected to an equivalent ground.

[0014] In one embodiment, the gain circuit further includes: a second operational amplifier, the positive input terminal of which is connected to the output terminal of the filter circuit, and the output terminal of which is connected to the input terminal of the signal processing module; a fifth resistor unit, the first terminal of which is connected to the negative input terminal of the second operational amplifier, and the second terminal of which is connected to an equivalent ground; and a sixth resistor unit, the first terminal of which is connected to the negative input terminal of the second operational amplifier, and the second terminal of which is connected to the output terminal of the second operational amplifier.

[0015] In one embodiment, the first resistor unit and the second resistor unit are high-precision low-temperature drift resistors, and the rate of change of the resistance value of the first resistor unit and the second resistor unit with temperature is less than a preset threshold.

[0016] The aforementioned gain circuit, by incorporating a logarithmic feedback loop (second feedback loop), effectively addresses the limited dynamic range issue inherent in traditional circuits. In the low-current region (signal less than or equal to the first threshold), the signal is amplified by the fixed-gain first feedback loop, ensuring the detectability of small signals. In the high-current region (signal greater than the first threshold), the conduction of the logarithmic feedback loop allows the circuit to adaptively adjust the gain, preventing signal saturation and significantly widening the circuit's dynamic range. When the input current exceeds the threshold, the conduction of the first diode unit introduces a logarithmic feedback mechanism, effectively preventing signal oversaturation under high-current conditions and ensuring signal integrity and the accuracy of subsequent processing. By introducing a flexible gain control strategy—a combination of fixed gain and logarithmic feedback gain—the signal processing capability of the pulse photoelectric detection device over a wide dynamic current range is significantly improved, solving the problem of limited range and inability to simultaneously handle both small and large current measurements inherent in traditional fixed-gain transimpedance amplifier circuits. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the gain circuit in one embodiment;

[0019] Figure 2 This is a gain curve diagram of the gain circuit in one embodiment;

[0020] Figure 3 This is a second schematic diagram of the gain circuit in one embodiment;

[0021] Figure 4 This is the third schematic diagram of the gain circuit in one embodiment;

[0022] Figure 5 This is the second gain curve diagram of the gain circuit in one embodiment;

[0023] Figure 6 This is the fourth schematic diagram of the gain circuit in one embodiment;

[0024] Figure 7 This is the fifth schematic diagram of the gain circuit in one embodiment. Detailed Implementation

[0025] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0029] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediary element. Furthermore, in the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if there is transmission of electrical signals or data between the connected objects.

[0030] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0031] As described in the background section, the range of signals that can be processed using related technologies is relatively limited, and the measurement results are not accurate enough when the signal varies greatly. The inventors discovered that this problem arises because, in Time-of-Flight (TOF) photoelectric detection technology, traditional pulse photoelectric detection devices mainly utilize fixed-gain current-to-voltage conversion circuits, that is, converting pulse current signals into voltage signals through operational amplifiers and transimpedance amplifiers. This technology is widely used for detecting the position and reflection properties of target objects, especially in lidar systems. In TOF lidar and various optical sensing applications, the detection and processing of photocurrents ranging from very weak (e.g., nanoamperes) to relatively strong (e.g., milliamperes) are often involved, and the intensity of the photocurrent directly reflects the distance and reflection properties of the target object. The methods in related technologies, due to their fixed gain, face significant limitations when processing a wide range of current signals. Fixed-gain transimpedance amplifiers are the most common signal conversion circuits in photoelectric detection; their main function is to convert the small current generated by the photodiode into a voltage signal for subsequent signal processing and data acquisition. The gain of this type of circuit is typically fixed, determined by the feedback resistor Rf of the transimpedance amplifier; that is, the relationship between the output voltage Vout and the input current Iin follows Vout = Iin * Rf. However, this fixed-gain design has an inherent problem: small current signals may not produce a sufficient voltage change to be detected, while large current signals may cause the circuit to saturate, resulting in the output voltage no longer linearly reflecting the input current, thus affecting the accuracy and reliability of the signal. Specifically, for small current signals (such as a few nanoamps), even with a high-resistance feedback resistor, the output voltage generated by the transimpedance amplifier may be too small to be effectively detected due to noise in the circuit. Conversely, for large current signals (such as a few milliamps), even with a low-resistance feedback resistor, the output voltage may be too high, causing the operational amplifier output to approach its power supply limits. This not only broadens the signal waveform but may also damage circuit components. Furthermore, large current signals may cause nonlinear effects in the photodiode, such as changes in the reverse recovery time and avalanche gain, all of which negatively impact signal integrity. Therefore, in related technologies, fixed-gain transimpedance amplifiers have limited range when dealing with photocurrents with a wide dynamic range, and cannot take into account both small and large current measurements, which limits the accuracy and reliability of photoelectric detection systems.

[0032] For the reasons mentioned above, this utility model provides a gain circuit that can adapt to a wide dynamic range current photoelectric detection circuit to provide a wider gain range and obtain accurate and reliable signal measurement results for signals of different sizes.

[0033] In one embodiment, such as Figure 1 As shown, a gain circuit is provided, including: a first operational amplifier U1, a first feedback loop 10, and a second feedback loop 20, wherein:

[0034] The positive input terminal of the first operational amplifier U1 is connected to the equivalent ground, and the inverting input terminal of the first operational amplifier U1 is used to receive the first signal.

[0035] Specifically, the first operational amplifier U1 plays a crucial signal amplification role in the pulsed photoelectric detection device. Its positive input terminal is typically connected to ground or a stable reference voltage to provide a zero-potential reference, enabling the inverting input terminal to accurately receive the signal. The inverting input terminal receives the first signal from the photogenerated current and amplifies it through an internal amplification mechanism. Due to the principles of virtual open and virtual short circuits, the potential of the inverting input terminal is almost the same as that of the positive input terminal, remaining near ground potential. This helps maintain circuit stability and reduce noise impact.

[0036] In this configuration, the positive input terminal (+) of the first operational amplifier U1 is connected to ground, the negative input terminal (-) is connected to the first signal input terminal, and the output terminal (Out) provides an amplified signal output. Simultaneously, the first operational amplifier U1, together with the first feedback loop 10 and the second feedback loop 20, constitute a complete signal amplification and conversion path.

[0037] The first end of the first feedback loop 10 is connected to the inverting input of the first operational amplifier U1, and the second end of the first feedback loop 10 is connected to the output of the first operational amplifier U1.

[0038] The first feedback loop 10 and the first operational amplifier U1 constitute a first gain circuit, which is used to provide a first gain for the first signal.

[0039] Specifically, one end of the first feedback loop 10 is connected to the inverting input of the first operational amplifier U1, and the other end is connected to the output of the first operational amplifier U1, forming a negative feedback closed loop. This connection method determines the relationship between the amplified output voltage and the input current, i.e., Vout1 = i * R1, where Vout1 is the output voltage, i is the input current, and R1 is the resistance value on the first feedback loop 10. When the input current is at a low level (less than or equal to the first threshold), the first feedback loop 10 dominates, providing a relatively fixed first gain to ensure the detectability of small signals.

[0040] In this circuit, the first resistor R1 is connected in series between the inverting input terminal and the output terminal of U1, forming the first feedback loop 10. Under low current conditions, the output of U1 is mainly determined by the resistance value of R1, thereby ensuring the stability of the signal amplification factor.

[0041] The first end of the second feedback loop 20 is connected to the inverting input of the first operational amplifier U1, and the second end of the second feedback loop 20 is connected to the output of the first operational amplifier U1. The second feedback loop 20 includes a first diode unit D1, which is connected in series between the first end and the second end of the second feedback loop 20.

[0042] When the first diode unit D1 is turned on, the second feedback loop 20, the first feedback loop 10, and the first operational amplifier U1 constitute a second gain circuit. The second gain circuit is used to provide a second gain for the first signal, and the first diode unit D1 is used to turn on when the absolute value of the first signal is greater than the first threshold.

[0043] Specifically, the second feedback loop 20 is composed of a first diode unit D1 and a resistor element connected in series. Its design aims to introduce logarithmic feedback characteristics when the current exceeds a certain threshold, addressing signal saturation or broadening under high current conditions. When the input current i is sufficiently large, such that i*R1 > VF (the turn-on voltage of the first diode unit D1), the first diode unit D1 conducts. At this time, the current is distributed between the first feedback loop 10 and the second feedback loop 20, forming two parts, i1 and i2. i1 forms a voltage through the first feedback loop 10, while i2 forms a voltage through the second feedback loop 20. This process makes the relationship between the overall output voltage Vout1 and the input current i more complex, no longer merely linear, but incorporating a logarithmic feedback component. This allows the signal to remain unsaturated under high current conditions while simultaneously expanding the circuit's dynamic range.

[0044] In this circuit, the first diode unit D1 and the resistor are connected in series to form the second feedback loop 20. The forward conduction characteristic of the first diode unit D1 determines whether the loop is conducting or not at a specific current threshold. When the first diode unit D1 is conducting, the voltage drop across the second feedback loop 20 combines with the voltage drop across the first feedback loop 10, affecting the output voltage of the first operational amplifier U1 and forming the second gain circuit.

[0045] In this embodiment, by adding a logarithmic feedback loop (second feedback loop) to the circuit, this solution effectively solves the problem of limited dynamic range in traditional circuits. In the low current range (signal less than or equal to the first threshold), the signal is amplified by the fixed-gain first feedback loop, ensuring the detectability of small signals. In the high current range (signal greater than the first threshold), the conduction of the logarithmic feedback loop enables the circuit to adaptively adjust the gain, preventing signal saturation and thus significantly widening the dynamic range of the circuit. When the input current exceeds the threshold, the conduction of the first diode unit introduces a logarithmic feedback mechanism, effectively preventing signal oversaturation under high current conditions, ensuring signal integrity and the accuracy of subsequent processing. By introducing a flexible gain control strategy, namely the combination of fixed gain and logarithmic feedback gain, the signal processing capability of the pulse photoelectric detection device in a wide dynamic current range is significantly improved, solving the problem of limited range and inability to simultaneously measure small and large currents in traditional fixed-gain transimpedance amplifier circuits.

[0046] In one embodiment, please see [link to previous article]. Figure 1 The first feedback loop 10 includes a first resistor unit R1. The first end of the first resistor unit R1 is connected to the inverting input terminal of the first operational amplifier U1, and the second end of the first resistor unit R1 is connected to the output terminal of the first operational amplifier U1.

[0047] Specifically, the first feedback loop 10 is composed of a first resistor unit R1, which is a key component for signal amplification in the circuit. It is connected between the inverting input and output terminals of the first operational amplifier U1, forming a closed-loop path. Through the first resistor unit R1, the first operational amplifier U1 can amplify the signal proportionally according to the magnitude of the input current, forming an output voltage Vout1. At lower current levels, the first resistor unit R1 ensures the linearity of signal conversion and amplification effect. At this time, the circuit behaves as a fixed-gain amplifier, and the output voltage Vout1 = i * R1, where i is the input current, Vout1 is the output voltage of the first operational amplifier U1, and R1 is the resistance value of the first resistor unit R1.

[0048] In this circuit, the first resistor unit R1 has its first end directly connected to the inverting input of the first operational amplifier U1, and its second end connected to the output of the first operational amplifier U1, forming a standard negative feedback path. In this circuit, the first resistor unit R1 undertakes the main task of signal amplification until the input current reaches a threshold sufficient to activate the second feedback loop 20.

[0049] The second feedback loop 20 further includes a second resistor unit R2. The first end of the second resistor unit R2 is connected to the first end of the first diode unit D1, the second end of the second resistor unit R2 is connected to the output terminal of the first operational amplifier U1, and the second end of the first diode unit D1 is connected to the inverting input terminal of the first operational amplifier U1.

[0050] Specifically, the second feedback loop 20 consists of a first diode unit D1 and a second resistor unit R2. In the circuit, the first diode unit D1 and the second resistor unit R2 are connected in series, forming a temperature-sensitive feedback path. When the input current i of the first signal is large enough that i*R1>VF (the forward conduction voltage of D1), D1 begins to conduct. At this time, part of the current flows through D1 and R2, forming i2, while the remaining current i1 continues to flow through R1 to form a voltage, i = i1 + i2. Due to the conduction of D1, the circuit enters a logarithmic feedback mode, and the output voltage Vout1 = i*R1*R2 / (R1+R2) + VF1*R1 / (R1+R2), where VF1 is the voltage across D1. R2 can be designed to be much smaller than R1, and the output voltage of the circuit can be approximated as Vout1 = i*R2 + VF1. This mechanism significantly improves the dynamic range of the circuit under high current conditions and avoids signal saturation or broadening problems. Schematic diagrams of fixed gain curves and composite gain curves are shown below. Figure 2 As shown.

[0051] In this circuit, the first terminal of the first diode unit D1 is connected to the first terminal of the second resistor unit R2, and the second terminal of D1 is directly connected to the inverting input terminal of the first operational amplifier U1. The second terminal of the second resistor unit R2 is connected to the output terminal of the first operational amplifier U1, forming a feedback path through D1 and R2. When D1 is turned on, the first feedback loop 10 and the second feedback loop 20 (D1 and R2) work together to amplify the composite gain of the signal in the first operational amplifier U1.

[0052] In this embodiment, at low current levels, the first resistor R1 serves as the core of the first feedback loop, ensuring a linear relationship between the input current and the output voltage. This allows the circuit to stably amplify small photocurrent signals without being affected by signal saturation. When the current reaches a certain threshold (i*R1>VF), the first diode unit D1 begins to conduct. At this time, the second feedback loop (D1 and R2) is activated, and the circuit's gain characteristic changes from linear to composite gain. That is, logarithmic feedback is introduced on the basis of the original amplification, avoiding signal saturation under high current conditions. At the same time, by adjusting the resistance value of R2, the amplification degree of the signal is further controlled, thereby achieving effective processing of high current signals and expansion of the dynamic range.

[0053] In one embodiment, such as Figure 3As shown, the gain circuit also includes: a first voltage sampling module 30 and a signal processing module 40, wherein:

[0054] The first voltage sampling module 30 is connected in parallel with the first diode unit D1 to collect the first voltage across the first diode unit D1 and convert the first voltage into a second signal output.

[0055] Specifically, the first voltage sampling module 30 is a circuit module designed to monitor and acquire the voltage across the first diode unit D1. It is connected in parallel with D1 to acquire the voltage change of D1 in the on-state, i.e., the first voltage VF1, in real time. This module can convert the acquired first voltage VF1 into a second signal suitable for subsequent processing. Typically, the second signal is a voltage or current signal proportional to VF1. In the circuit, the first voltage sampling module 30 implements the voltage conversion process across D1 through an independent operational amplifier (U3) or voltage follower, ensuring signal isolation and linearity of the conversion. This conversion is necessary because directly using the voltage across D1 may not be suitable for further signal processing or calculation, especially in cases requiring high-precision measurements or temperature compensation.

[0056] In the circuit diagram, the first voltage sampling module 30 may include an additional operational amplifier U3, whose positive input terminal is connected to the anode of D1 and its negative input terminal is connected to the cathode of D1, thus forming a voltage acquisition circuit connected in parallel across D1. The output terminal of U3 will output a second signal, which is a linear conversion of VF1, facilitating calculation and analysis by the subsequent signal processing module 40.

[0057] The signal processing module 40 is connected to the output terminals of the first voltage sampling module 30 and the first operational amplifier U1, respectively. When the first diode unit D1 is turned on, it subtracts the second signal from the third signal output by the first operational amplifier U1 to obtain the second voltage across the second resistor unit. The second voltage is used to indicate the parameters of the first signal.

[0058] Specifically, the signal processing module 40 is the core part of the entire system responsible for signal processing and calculation. It receives the third signal (i.e., the amplified signal) output from the first operational amplifier U1 and the second signal (i.e., the converted signal of the voltage across D1) output from the first voltage sampling module 30. With D1 conducting, it performs a subtraction operation to obtain the second voltage across the second resistor unit, i.e., i2*R2. This second voltage directly reflects the parameter information of the first signal under high current conditions and is crucial data for determining signal strength and preventing signal saturation. Through this calculation, the signal processing module 40 can accurately acquire signal information under high current conditions without being affected by the temperature drift of the logarithmic feedback loop.

[0059] In this embodiment, when the first signal is greater than the first threshold, the first diode unit D1 begins to conduct. At this time, the VF1 collected by the first voltage sampling module 30 includes the influence of temperature changes that the first diode unit D1 may be affected by. However, by subtracting the second signal (the conversion of VF1) from the third signal (the amplified signal) by the signal processing module 40, the current i2 through the second resistor unit R2, i.e., the second voltage i2*R2, can be accurately obtained, thereby avoiding signal saturation and broadening under large current and ensuring the integrity and accuracy of the signal. Since the first voltage VF1 (the voltage across D1) is greatly affected by temperature changes, directly using it for signal processing may introduce errors. However, by using the subtraction operation of the signal processing module 40, the influence of temperature changes in the first voltage can be eliminated, thereby obtaining a relatively pure signal representation, i.e., the second voltage i2*R2, used to indicate the parameters of the first signal (i.e., the photocurrent), which is not affected by temperature changes. The design of the signal processing module 40 allows the system to perform real-time calculations based on the third signal output from the first operational amplifier U1 and the second signal output from the first voltage sampling module 30. This flexibility enhances the system's adaptability to various signal conditions, especially in scenarios requiring dynamic gain adjustment to accommodate different current levels. Through the collaboration of the first voltage sampling module 30 and the signal processing module 40, the system can accurately measure signals under high current conditions, while improving the accuracy and reliability of signal processing through temperature-induced compensation. This approach not only expands the dynamic range of the circuit but also ensures the stability and accuracy of the signal under any operating conditions, significantly improving the overall performance and applicability of the photoelectric detection device.

[0060] In one embodiment, such as Figure 4 As shown, the gain circuit also includes a third feedback loop. The third feedback loop includes a third resistor unit R3 and a second diode unit (D2+D3).

[0061] In this configuration, the first end of the third resistor unit R3 is connected to the first end of the second diode unit, the second end of the third resistor unit R3 is connected to the output terminal of the first operational amplifier U1, and the second end of the second diode unit is connected to the inverting input terminal of the first operational amplifier U1.

[0062] The second diode unit is used to conduct when the absolute value of the first signal is greater than a second threshold, and the second threshold is greater than the first threshold.

[0063] Specifically, the third feedback loop is a component in the circuit used to further extend the dynamic range and handle higher intensity photocurrents. It consists of a third resistor unit R3 and a second diode unit (D2+D3), where the threshold voltage (turn-on voltage) of (D2+D3) is higher than that of D1 (the first diode unit D1). This means that (D2+D3) will only conduct when the photocurrent increases further, causing the absolute value of the first signal to exceed the second threshold. The purpose of this design is to provide additional control for high-current conditions, preventing signal distortion or saturation under extreme conditions.

[0064] In this circuit, the first terminal of the third resistor unit R3 is connected to the first terminal of the second diode unit (D2+D3). The second terminal of R3 is connected to the output terminal of the first operational amplifier U1. The second terminal of (D2+D3) is directly connected to the inverting input terminal of U1, forming a series feedback loop. When the strength of the first signal does not exceed the second threshold of (D2+D3), (D2+D3) is in the off state and has no effect on the circuit. However, once the signal strength is sufficient to turn on (D2+D3), it forms a new current path, which works in parallel with the first and second feedback loops. Figure 5 As shown, when the strength of the first signal is less than the first threshold VF, only the first feedback loop of the gain circuit is turned on. When the strength of the first signal is greater than the first threshold VF but less than the second threshold VF2, the first and second feedback loops of the gain circuit are turned on. When the strength of the first signal is greater than the second threshold VF2, the first, second, and third feedback loops of the gain circuit are turned on, making the gain curve smoother and achieving the effect of dynamically widening the range. The calculation formula principle is the same as above and will not be repeated.

[0065] In this embodiment, by adding a third feedback loop to the circuit, this solution can effectively handle current signals higher than the first threshold. When the absolute value of the first signal exceeds the turn-on voltage (second threshold) of the second diode unit, the second diode unit begins to conduct. At this time, the circuit enters a higher-level logarithmic feedback mode, which can better control and amplify extremely high-intensity photogenerated current signals, avoid signal saturation, and thus further widen the dynamic range of the circuit. In the circuit design, the first, second, and third feedback loops form a multi-level gain control system. As the current input current increases, the circuit automatically switches to a more suitable gain mode, ensuring that the signal is accurately amplified and undistorted regardless of changes in signal strength. The second diode unit may also be affected by temperature changes, but in the circuit design, by setting the second threshold higher than the first threshold, even under high-temperature drift conditions, the conduction of the second diode unit will not easily occur unless the current intensity reaches an extremely high level. This design ensures that within the normal operating range, even if the ambient temperature rises, the main signal processing of the circuit is still dominated by the first and second feedback loops, thereby maintaining high signal processing stability and consistency. The introduction of the third feedback loop also provides a circuit protection mechanism to prevent overload or damage to the first two stages of the circuit (the first and second feedback loops) under extremely high current input conditions. The conduction of the second diode unit ensures that even if the input current far exceeds the normal operating range, the circuit can still avoid damage to critical components through appropriate gain adjustment, extending the lifespan of the equipment. By adding the third feedback loop, this scheme achieves control and management of extremely high-intensity photocurrent signals, not only further expanding the dynamic range of the circuit but also improving the efficiency and safety of the photoelectric detection device in handling a wide dynamic current range through multi-stage gain control and improved temperature stability.

[0066] In one embodiment, please see [link to previous article]. Figure 4 The gain circuit also includes: a second voltage sampling module U4.

[0067] The second voltage sampling module U4 is connected in parallel with the second diode unit (D2+D3) to collect the third voltage across the second diode unit and convert the third voltage into a fourth signal output.

[0068] Specifically, the function of the second voltage sampling module U4 is to acquire the third voltage across the second diode unit in real time when the second diode unit is conducting, and convert it into a fourth signal output. The inclusion of this module ensures that the system can accurately acquire the voltage state of the second diode unit even under extremely high current conditions, providing crucial data for subsequent signal processing. This module may contain a high-precision voltage follower or operational amplifier to convert the third voltage into a easily processed fourth signal, such as a voltage or current signal.

[0069] The second voltage sampling module U4 may consist of a high-precision operational amplifier U4, with its positive input connected to the anode of the second diode unit and its negative input connected to the cathode of the second diode unit, forming a voltage acquisition circuit in parallel with the second diode unit. The output of U4 will output a fourth signal, which is a converted signal of the third voltage and can directly reflect the voltage change of the second diode unit in the conducting state.

[0070] The signal processing module 40 is also connected to the second voltage sampling module U4, and is used to subtract the fourth signal from the third signal received from the first operational amplifier U1 when the second diode unit is turned on, so as to obtain the fourth voltage across the third resistor unit R3, wherein the fourth voltage is used to indicate the parameters of the first signal.

[0071] Specifically, the signal processing module 40 not only processes data from the first voltage sampling module 30, but is also further connected to the second voltage sampling module U4. When the second diode unit is turned on, it can subtract the fourth signal (the converted signal of the third voltage) from the third signal (the amplified signal) output by the first operational amplifier U1, thereby obtaining the fourth voltage Vout4 across the third resistor unit R3. This operation is to analyze the signal parameters under extremely high current conditions, ensuring that the system's signal measurement is accurate across any dynamic range, unaffected by the temperature drift state of the second diode unit in the logarithmic feedback loop.

[0072] In this embodiment, the combined use of the second voltage sampling module and the signal processing module 40 enables the system to accurately analyze signal parameters under extremely high current conditions. When the absolute value of the first signal exceeds the second threshold of the second diode unit, the second diode unit conducts. At this time, by acquiring the third voltage and converting it into a fourth signal, the signal processing module 40 can eliminate the influence of the logarithmic feedback loop on the original signal and obtain the fourth voltage across the third resistor unit R3. This voltage directly reflects the signal strength under extreme high current conditions and is not affected by the nonlinear temperature drift of the second diode unit. In the system design, layered gain control is achieved through the first diode unit D1, the second diode unit, and their respective sampling modules. Under different current intensities, the system automatically switches to the most suitable gain mode, ensuring accurate signal amplification under small current, large current, or extreme high current conditions, avoiding signal saturation or broadening, and improving the flexibility and efficiency of signal processing. The third voltage of the second diode unit may also be affected by temperature changes. However, by performing a subtraction operation between the third and fourth signals using the signal processing module 40, the system can eliminate the influence of temperature changes on signal processing. This ensures that the fourth voltage accurately reflects the parameters of the first signal under any temperature conditions, improving the system's temperature stability and signal processing accuracy. With the second diode unit conducting, the fourth voltage obtained by the signal processing module 40 through subtraction not only reflects the signal strength under extremely high current conditions but also maintains signal integrity. This processing method ensures that even when the signal strength is extremely high, the system can still provide accurate and stable signal output, enhancing the data reliability and performance stability of the photoelectric detection device.

[0073] In one embodiment, such as Figure 6 As shown, the signal processing module 40 includes: an analog-to-digital converter 41 and a processor 42, wherein:

[0074] The analog-to-digital converter 41 is connected to the output terminals of the first voltage sampling module 30 and the first operational amplifier U1, respectively, and is connected to the reference voltage. The analog-to-digital converter 41 is used to output the corresponding level signal according to the magnitude relationship between the second voltage and the reference voltage.

[0075] Specifically, the analog-to-digital converter (ADC) 41 is a key component of the circuit, responsible for converting continuous analog signals into discrete digital signals for analysis and processing by the processor 42. In this design, the ADC is connected to the outputs of the first voltage sampling module 30 and the first operational amplifier U1, and is also connected to a reference voltage source. The ADC works by comparing the input analog signal with the reference voltage, and outputting corresponding level signals based on the magnitude relationship between the two. These level signals represent the digital code of the input signal. In particular, the ADC compares the received second voltage with the reference voltage and outputs a level signal corresponding to the second voltage value.

[0076] The processor 42 is connected to the output of the analog-to-digital converter 41. The processor 42 is used to analyze the level signal to determine the target current value indicated by the first signal, and to obtain the reflection parameter corresponding to the first signal according to the correspondence between the target current value and the preset current value and reflection parameter.

[0077] Specifically, the processor 42 is the control and data analysis center of the entire photoelectric detection device. Connected to the output of the ADC, it extracts information from the level signals received by the ADC and analyzes these digital signals using a built-in algorithm to determine the target current value indicated by the first signal (i.e., the original photocurrent signal). Based on calibrated data, the processor 42 uses a preset correspondence between the current value and reflection parameters to calculate the reflection parameters corresponding to the first signal, thereby determining the position information and reflection properties of the target object. This processing method ensures that even weak or extremely strong photocurrent signals can be accurately interpreted by the processor 42.

[0078] In this embodiment, the analog signal is converted into a digital signal by an ADC. The processor 42 can accurately analyze these signals, unaffected by fluctuations in the analog signal, ensuring the accuracy and reliability of signal processing. The ADC can handle various signal intensities (from weak small current signals to large current signals in a saturated state) from the first voltage sampling module 30 and the first operational amplifier U1, and through the algorithm adjustment of the processor 42, it adapts to the wide dynamic range of the photoelectric detection device, maintaining accurate signal analysis even under extreme conditions. Based on the correspondence between the calibrated current value and the reflection parameter, the processor 42 can directly calculate the reflection parameter of the target object from the level signal output by the ADC. This process skips the complex signal reconstruction stage, improving the speed and accuracy of signal processing. The processor 42 can not only analyze the reflection parameter in the signal, but also compensate for deviations caused by temperature changes during signal processing through a built-in algorithm, ensuring that the measurement results of the reflection parameter are consistent and accurate under different temperature environments.

[0079] In one embodiment, such as Figure 7 As shown, the gain circuit also includes a filter circuit 60. The filter circuit 60 is connected in series between the output terminal of the first operational amplifier U1 and the signal processing module 40. The input terminal of the filter circuit 60 is connected to the output terminal of the first operational amplifier U1, and the output terminal of the filter circuit 60 is connected to the input terminal of the signal processing module 40. The filter circuit 60 is used to filter out the DC component and the low-frequency component with a frequency lower than the preset cutoff frequency in the third signal output by the first operational amplifier U1.

[0080] Specifically, the function of the filter circuit 60 here is to preprocess the signal output by the first operational amplifier U1. Specifically, it filters out the DC component and low-frequency noise below a preset cutoff frequency from the signal to ensure that the signal processing module 40 can receive a clear, interference-free AC signal. This type of filter circuit 60 is commonly referred to as a high-pass filter; it blocks signals below a certain frequency while allowing signals above that frequency to pass through smoothly.

[0081] In one exemplary embodiment, please continue to see Figure 7 The filter circuit 60 includes: a first capacitor unit C1 and a fourth resistor unit R4, wherein:

[0082] The first end of the first capacitor unit C1 is connected to the output end of the first operational amplifier U1, and the second end of the first capacitor unit C1 is connected to the input end of the signal processing module 40.

[0083] The first end of the fourth resistor unit R4 is connected to the second end of the first capacitor unit C1, and the second end of the fourth resistor unit R4 is connected to the equivalent ground.

[0084] Specifically, the first capacitor unit C1 and the fourth resistor unit R4 constitute a simple RC high-pass filter. The first end of C1 is directly connected to the output of the first operational amplifier U1, receiving the amplified signal (the third signal). The second end of C1 is connected to the input of the signal processing module 40 through R4, so that the signal processing module 40 can only receive the filtered signal, that is, the signal after filtering out DC and low-frequency components. In addition, the other end of R4 (i.e., the second end) should be grounded or equivalently connected to the ground plane of the circuit to complete the loop of the filter circuit 60. C1 plays the role of blocking DC signals and low-frequency signals from passing through, while R4 determines the cutoff frequency of the filter circuit 60. According to circuit theory, the cutoff frequency fc of the RC high-pass filter can be calculated by the formula fc = 1 / (2*π*R*C). In this design, the combination of R4 and C1 ensures that the signal processing module 40 only receives signals higher than the preset cutoff frequency, thereby removing unnecessary DC components and low-frequency noise.

[0085] In this embodiment, the filter circuit 60 effectively filters out the DC component and low-frequency noise in the signal, ensuring that the signal processing module 40 receives a pure AC signal and improving the accuracy of signal processing. After removing DC and low-frequency noise, the signal processed by the signal processing module 40 is no longer affected by these components, reducing signal distortion and improving the signal's authenticity and reliability. The use of the filter circuit 60 not only removes unnecessary signal components but also optimizes the signal bandwidth, allowing the system to focus more on processing rapidly changing signals, which is particularly important for enhancing the dynamic range of the photoelectric detection device.

[0086] In one embodiment, please see [link to previous article]. Figure 7 The gain circuit also includes: a second operational amplifier U2, a fifth resistor unit R5, and a sixth resistor unit R6, wherein:

[0087] The positive input terminal of the second operational amplifier U2 is connected to the output terminal of the filter circuit 60, and the output terminal of the second operational amplifier U2 is connected to the input terminal of the signal processing module 40.

[0088] Specifically, the main function of the second operational amplifier U2 is to further amplify and buffer the signal processed by the filter circuit 60, ensuring that the signal has sufficient level and stability when transmitted to the signal processing module 40. In this technical solution, the positive input terminal of U2 receives the clean signal output by the filter circuit 60, while its output terminal is directly connected to the input terminal of the signal processing module 40, preparing for subsequent signal analysis.

[0089] The first end of the fifth resistor unit R5 is connected to the negative input terminal of the second operational amplifier U2, and the second end of the fifth resistor unit R5 is connected to the equivalent ground.

[0090] The first end of the sixth resistor unit R6 is connected to the negative input terminal of the second operational amplifier U2, and the second end of the sixth resistor unit R6 is connected to the output terminal of the second operational amplifier U2.

[0091] Specifically, the fifth resistor unit R5 and the sixth resistor unit R6 form a negative feedback loop at the second operational amplifier U2. R5 is connected between the negative input terminal of U2 and circuit ground, while R6 is connected between the negative input terminal and the output terminal of U2. This negative feedback design can stabilize the output of the second operational amplifier U2, reduce nonlinear distortion, and may adjust the amplifier gain to better suit the needs of subsequent signal processing.

[0092] For example, due to the virtual shorting effect of the second operational amplifier U2, the output of the second operational amplifier U2 is Vout2 = R1 * i1 * (1 + R6 / R5). When the temperature changes, VF1 of the first diode unit D1 experiences temperature drift. According to Ohm's law i = i1 + i2, where i1 is the current in the first feedback loop and i2 is the current in the second feedback loop, the currents i1 and i2 can still be accurately measured by acquiring the output Vout2 of the second operational amplifier U2 and the second signal Vdiff output by the first voltage sampling module 30. Here, i1 = Vout2 / (1 + R6 / R5) / R1, i2 = (Vout2 / (1 + R6 / R5) - Vdiff / A) / R2, where A is the gain of the first voltage sampling module 30, and Vdiff / A is the voltage across the first diode unit D1.

[0093] In this embodiment, the second operational amplifier amplifies the filtered signal to ensure sufficient strength when transmitted to the signal processing module. The negative feedback loop formed by the fifth resistor unit R5 and the sixth resistor unit R6 adaptively adjusts the output signal level, improving signal stability during amplification, reducing distortion, and ensuring signal linearity and accuracy. The ratio of the fifth resistor unit R5 to the sixth resistor unit R6 directly affects the gain of the second operational amplifier. This design allows for fine-tuning of the amplifier's gain based on signal characteristics and the requirements of the downstream signal processing module, thereby optimizing the overall system's signal dynamic range and processing capabilities. The output signal from the filtering circuit has already had its DC component and most low-frequency noise removed before entering the second operational amplifier. The amplification and negative feedback mechanism of the second operational amplifier further reduce random noise and interference in the signal, improving signal clarity and quality. The second operational amplifier and the negative feedback circuit ensure that the signal processing module receives a high-quality, stable signal. This not only improves the efficiency of the signal processing module but also increases its ability to accurately analyze signals. For photoelectric detection systems, this translates to higher measurement accuracy and reliability.

[0094] In one embodiment, the first resistor unit and the second resistor unit are high-precision low-temperature drift resistors, and the rate of change of the resistance value of the first resistor unit and the second resistor unit with temperature is less than a preset threshold.

[0095] Specifically, in this application, the first resistor unit R1 and the second resistor unit R2 use high-precision low-temperature drift resistors. Low-temperature drift resistors are those whose resistance value changes very little with temperature variations, typically at a rate less than a preset threshold. This type of resistor is crucial in precision circuit design because it reduces signal errors caused by ambient temperature fluctuations, improving circuit stability and reliability. Using high-precision low-temperature drift resistors, especially in temperature-sensitive signal paths, ensures that the resistance value remains constant over a wide temperature range, thereby preventing signal amplitude and gain from being affected by temperature changes.

[0096] Specifically, all operational amplifiers in this application (such as the first operational amplifier U1, the second operational amplifier U2, etc.) are designed as high-precision, low-temperature-drift operational amplifiers. Low-temperature-drift operational amplifiers can maintain the consistency of their amplification characteristics at different temperatures, reducing the impact of temperature changes on amplifier gain and bias point. In signal processing circuits, operational amplifiers are critical components, and their performance directly affects the amplification accuracy of the signal and the overall stability of the signal chain. Using low-temperature-drift operational amplifiers ensures stable signal gain over a wide temperature range, reducing nonlinear distortion and noise in signal processing.

[0097] Specifically, the analog-to-digital converter (ADC) and its reference voltage source also utilize high-precision, low-temperature-drift types. The ADC is used to convert analog signals into digital signals, and its resolution and accuracy are crucial to the performance of the photoelectric detection system. Low-temperature-drift ADCs and reference voltages can maintain the accuracy of signal conversion despite temperature variations, reducing conversion errors and ensuring the accuracy and consistency of the digital signal.

[0098] In this embodiment, high-precision, low-temperature-drift resistors are used as the basic components of the circuit, significantly reducing the impact of temperature changes on circuit performance. In photoelectric detection equipment, the measurement of photocurrent often requires high precision; even minute temperature changes can lead to measurement errors. By using low-temperature-drift resistors, signal gain and amplitude stability can be maintained over a wide temperature range, which is crucial for improving the temperature adaptability and long-term reliability of the equipment. High-precision, low-temperature-drift operational amplifiers ensure the consistency of signal processing at different temperatures, reducing nonlinear distortion and noise introduction in the signal chain, thus improving the accuracy and reliability of signal processing. This is indispensable for photoelectric detection systems that need to accurately capture and resolve weak signals in changing environments, improving the overall system performance and measurement accuracy. Using high-precision, low-temperature-drift ADCs and reference voltages maintains the accuracy and consistency of analog-to-digital conversion when temperatures change, which is particularly important for systems requiring precise reflection time measurements. This ensures that the digital representation of the signal remains accurate even in temperature-changing environments, improving the reliability of system data and the repeatability of measurements. All key components are designed with low-temperature-drift characteristics, significantly improving the system's adaptability to temperature changes, reducing the impact of temperature fluctuations on signal processing, and improving the system's temperature stability.

[0099] In the description of this specification, references to terms such as "some embodiments," "other embodiments," and "ideal embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0100] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0101] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A gain circuit, characterized in that, include: A first operational amplifier, wherein the positive input terminal of the first operational amplifier is connected to an equivalent ground, and the inverting input terminal of the first operational amplifier is used to receive a first signal; A first feedback loop, wherein a first end of the first feedback loop is connected to the inverting input terminal of the first operational amplifier, and a second end of the first feedback loop is connected to the output terminal of the first operational amplifier, wherein the first feedback loop and the first operational amplifier constitute a first gain circuit, and the first gain circuit is used to provide a first gain for the first signal. The second feedback loop has a first end connected to the inverting input of the first operational amplifier and a second end connected to the output of the first operational amplifier. The second feedback loop includes a first diode unit connected in series between the first and second ends of the second feedback loop. When the first diode unit is turned on, the second feedback loop, the first feedback loop, and the first operational amplifier constitute a second gain circuit. The second gain circuit is used to provide a second gain for the first signal. The first diode unit is used to turn on when the absolute value of the first signal is greater than a first threshold.

2. The gain circuit according to claim 1, characterized in that, The first feedback loop includes: a first resistor unit, a first end of which is connected to the inverting input terminal of the first operational amplifier, and a second end of which is connected to the output terminal of the first operational amplifier; The second feedback loop further includes: a second resistor unit, the first end of which is connected to the first end of the first diode unit, the second end of which is connected to the output terminal of the first operational amplifier, and the second end of the first diode unit is connected to the inverting input terminal of the first operational amplifier.

3. The gain circuit according to claim 2, characterized in that, The gain circuit also includes: A first voltage sampling module is connected in parallel with the first diode unit, used to collect a first voltage across the first diode unit and convert the first voltage into a second signal output. The signal processing module is connected to the output terminals of the first voltage sampling module and the first operational amplifier, respectively. When the first diode unit is turned on, the module subtracts the second signal from the third signal output by the first operational amplifier to obtain the second voltage across the second resistor unit. The second voltage is used to indicate the parameters of the first signal.

4. The gain circuit according to claim 3, characterized in that, The gain circuit further includes a third feedback loop, which includes a third resistor unit and a second diode unit. The first end of the third resistor unit is connected to the first end of the second diode unit, the second end of the third resistor unit is connected to the output terminal of the first operational amplifier, and the second end of the second diode unit is connected to the inverting input terminal of the first operational amplifier. The second diode unit is used to conduct when the absolute value of the first signal is greater than a second threshold, and the second threshold is greater than the first threshold.

5. The gain circuit according to claim 4, characterized in that, The gain circuit also includes: The second voltage sampling module is connected in parallel with the second diode unit and is used to collect the third voltage across the second diode unit and convert the third voltage into a fourth signal output. The signal processing module is also connected to the second voltage sampling module and is used to subtract the fourth signal from the third signal received from the first operational amplifier when the second diode unit is turned on, so as to obtain the fourth voltage across the third resistor unit, wherein the fourth voltage is used to indicate the parameters of the first signal.

6. The gain circuit according to claim 3, characterized in that, The signal processing module includes: An analog-to-digital converter (ADC) is connected to the output terminals of the first voltage sampling module and the first operational amplifier, respectively, and is connected to a reference voltage. The ADC is used to output a corresponding level signal according to the magnitude relationship between the second voltage and the reference voltage. The processor is connected to the output of the analog-to-digital converter. The processor is used to analyze the level signal to determine the target current value indicated by the first signal, and to obtain the reflection parameter corresponding to the first signal according to the target current value and the correspondence between the preset current value and the reflection parameter.

7. The gain circuit according to claim 3, characterized in that, The gain circuit also includes: A filtering circuit is connected in series between the output terminal of the first operational amplifier and the signal processing module. The input terminal of the filtering circuit is connected to the output terminal of the first operational amplifier, and the output terminal of the filtering circuit is connected to the input terminal of the signal processing module. The filtering circuit is used to filter out the DC component and the low-frequency component with a frequency lower than a preset cutoff frequency in the third signal output by the first operational amplifier.

8. The gain circuit according to claim 7, characterized in that, The filtering circuit includes: The first capacitor unit has a first end connected to the output terminal of the first operational amplifier and a second end connected to the input terminal of the signal processing module. A fourth resistor unit, wherein the first end of the fourth resistor unit is connected to the second end of the first capacitor unit, and the second end of the fourth resistor unit is equivalently connected.

9. The gain circuit according to claim 7, characterized in that, The gain circuit also includes: A second operational amplifier, the positive input of which is connected to the output of the filter circuit, and the output of which is connected to the input of the signal processing module; The fifth resistor unit has its first end connected to the negative input terminal of the second operational amplifier, and its second end connected to the equivalent ground. The sixth resistor unit has its first end connected to the negative input terminal of the second operational amplifier, and its second end connected to the output terminal of the second operational amplifier.

10. The gain circuit according to any one of claims 2-9, characterized in that, The first resistor unit and the second resistor unit are high-precision low-temperature drift resistors, and the rate of change of the resistance value of the first resistor unit and the second resistor unit with temperature is less than a preset threshold.

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