SAPD-oriented weak current and avalanche voltage pulse sampling system

Abstract

The invention discloses an SAPD-oriented weak current and avalanche voltage pulse sampling system. The system comprises a power supply module, a detection sampling module and a control processing module. The power supply module provides working voltage for the detection sampling module and the control processing module. The control processing module receives a control instruction from an upper computer, communicates with the detection sampling module through an I / O interface, switches the working mode of the SAPD sensor, receives a sampling signal output by the sampling processing circuit, and transmits sampling information back to the upper computer. The detection sampling module can control a peripheral circuit through a program control instruction of an upper computer, so that the SAPD can be switched between a linear mode and a Geiger mode, the SAPD sensor is switched to be connected with the linear sampling processing circuit or the Geiger sampling processing circuit through the mode conversion circuit, full-voltage range scanning is carried out on the SAPD sensor, and the SAPD sensor is connected with the linear sampling processing circuit or the Geiger sampling processing circuit. And full working domain range sampling of the SAPD is realized.

Description

Technical Field

[0001] This invention belongs to the field of high-precision measurement technology and relates to the sampling and measurement of weak signals, specifically to a weak current and avalanche voltage pulse sampling system for SAPD. Background Technology

[0002] Silicon carbide avalanche diodes (SAPDs) are high-performance photodetectors. Depending on the operating voltage, most SAPDs operate under reverse bias and can be divided into two operating modes: (1) When the reverse bias voltage of the SAPD is lower than its avalanche voltage, the SAPD linearly amplifies the incident photoelectrons, i.e., in linear mode, generating photocurrents from nanoamperes to microamperes. (2) When the reverse bias voltage of the SAPD reaches its avalanche voltage, its gain increases rapidly, reaching 10... 5 ~10 6 At this point, the absorption of a single photon is sufficient to saturate the output current, i.e., Geiger mode. In Geiger mode, the electric field of the pn junction of the SAPD is very high, and photogenerated electrons and holes collide and ionize, causing the SAPD current to continuously increase, resulting in a self-sustaining avalanche multiplication process. Therefore, an SAPD operating in Geiger mode can trigger a high avalanche current and generate a voltage pulse at the milliampere level as long as there are a few photogenerated carriers in the multiplication layer. Thus, the SAPD can achieve weak light detection or even single-photon detection. Compared with traditional silicon-based avalanche photodiodes (APDs), SAPDs have a wider bandgap and higher thermal stability, maintaining excellent performance even in extreme environments. In addition, SAPDs also have fast response times and low dark current, and are widely used in signal amplification and detection in optical communication systems, as well as high-precision photoelectric detection in fields such as biomedical imaging, environmental monitoring, and space exploration.

[0003] To achieve SAPD-based detection, it is necessary to sample the weak signals generated at the nanoampere or even picoampere level. These signals are inherently weak and difficult to detect, requiring amplification. However, since these weak signals are on the same order of magnitude or even weaker than parameters such as leakage current and bias current of the device, they can couple with noise such as electric or magnetic fields during transmission and conditioning, resulting in a low signal-to-noise ratio for the current signal, or even being overwhelmed by noise.

[0004] Prior art 1 (CN109782142A) discloses a partial discharge detection device and system for GIS (Gas Insulated Metal Enclosed Switchgear). It utilizes a SAPD as an optical sensor, applying a reverse bias to the SAPD to enable it to operate in Geiger mode. Upon detecting a light signal, it generates an avalanche current, achieving a highly sensitive GIS partial discharge detection device. Prior art 2 (CN113720447B) discloses a gated silicon-based visible-near-infrared single-photon detection device. It utilizes an FPGA, a high-speed CMOS driver, and an RF transformer to adjust the pulse width, frequency, and amplitude, generating a high-voltage gated pulse with short rise and fall times. This improves single-photon detection efficiency, reduces dark counting and after-pulse probability, and filters out spike noise caused by the leading and trailing edges of the gated pulse, thus achieving avalanche signal counting.

[0005] However, due to manufacturing process limitations, even SAPDs from the same manufacturer and batch can exhibit differences in electrical performance, with variations in parameters such as avalanche voltage, responsivity, and quantum efficiency. Furthermore, while SAPDs operate within a 0V to 200V voltage range, their operating current range is extremely narrow, typically not exceeding 1mA. This necessitates stringent requirements for bias voltage supply schemes and current-limiting protection schemes. When using a single SAPD as a detection sensor, the detection device needs recalibration to adapt to the SAPD. Some detection devices are even only compatible with SAPDs manufactured using specific processes and models. If a new SAPD is to be used for detection and sampling, a completely new detection circuit system must be replaced or designed to adapt it. Additionally, when the measured optical power is high, the SAPD only needs to operate in the linear region to detect the photocurrent, while when the measured optical power is low, the SAPD needs to operate in the Geiger region to detect the number of avalanche pulses. Current technology lacks a solution for switching the operating modes of the SAPD. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a weak current and avalanche voltage pulse sampling system for SAPDs. The system can control the peripheral circuits via host computer programmable commands, enabling the SAPD to switch between linear and Geiger modes. Simultaneously, it can perform full voltage range scanning of the SAPD within the system, achieving full operating range sampling of the SAPD.

[0007] A weak current and avalanche voltage pulse sampling system for SAPD includes a power supply module, a detection and sampling module, and a control and processing module.

[0008] The power module is connected to an AC power source via a power adapter to charge the lithium battery pack or provide operating voltage for the detection sampling module and the control processing module.

[0009] The detection and sampling module includes a reverse connection protection circuit, a voltage conversion circuit, an SAPD sensor, a mode conversion circuit, a linear sampling processing circuit, and a Geiger sampling processing circuit. The voltage conversion circuit is connected to the output of the power supply module via the reverse connection protection circuit, converting the power supply module's output voltage into different operating voltages to power the SAPD sensor, the linear sampling processing circuit, and the Geiger sampling processing circuit. The mode conversion circuit switches the connection between the SAPD sensor and either the linear or Geiger sampling processing circuit according to instructions from the control processing module. The linear and Geiger sampling processing circuits receive the output signal from the SAPD sensor, process it, and return the processed signal to the control processing module.

[0010] The linear sampling processing circuit employs a two-stage amplification scheme. First, the weak photocurrent output from the positive electrode of the SAPD sensor is converted into a voltage and amplified by a transimpedance amplifier circuit. Then, it is further discharged through a multiplexer and an operational amplifier circuit. The control terminal of the multiplexer is connected to the control processing module, and different resistance levels are selected according to the instructions of the control processing module to change the amplification factor of the inverting proportional amplifier circuit.

[0011] The Geiger sampling and processing circuit includes a DAC circuit, an amplifier circuit, a comparator circuit, and a quenching circuit. The amplifier circuit amplifies the avalanche voltage pulse signal output from the positive terminal of the SAPD sensor. The DAC circuit provides an adjustable reference voltage to the comparator circuit according to instructions from the control processing module. The comparator circuit compares the signal output from the amplifier circuit with the reference voltage and outputs the comparison result to the control processing module. The quenching circuit is used to quench the current and reset the SAPD sensor in the activated state.

[0012] The control processing module uses an FPGA as the control chip, receives control commands from the host computer, communicates with the detection and sampling module through the I / O interface, switches the working mode of the SAPD sensor, receives the sampling signal output by the sampling processing circuit, and transmits the sampling information back to the host computer.

[0013] Preferably, the control processing module further includes a hardware noise reduction module. The hardware noise reduction module filters out high-frequency glitches in the sampled signal output by the sampling processing circuit through a combination of RC low-pass filtering and second-order active filtering, and uses a Schmitt trigger to set a hysteresis threshold shaping signal, combined with a monostable multivibrator to identify the pulse width.

[0014] Preferably, the host computer uses a baseline detection dynamic threshold algorithm, combined with median filtering and pulse correlation detection to remove isolated noise pulses from the sampling information returned by the control processing module, and uses Kalman filtering to establish a signal state model to predict and correct noise interference.

[0015] In linear mode, the voltage conversion circuit, under the control of the control processing module, provides a bias voltage less than the avalanche voltage to the SAPD sensor, and samples the weak photocurrent signal output by the SAPD sensor through the linear sampling processing circuit. In Geiger mode, the voltage conversion circuit, under the control of the control processing module, provides a bias voltage greater than the avalanche voltage to the SAPD sensor, and uses the Geiger sampling processing circuit to sample the weak avalanche voltage pulse signal output by the SAPD sensor.

[0016] The present invention has the following beneficial effects: 1. Provides 10V~200V stepless adjustable bias voltage power supply for SAPD: Using a non-isolated fly-back circuit series high-voltage LDO combined with digital positioner circuit, it realizes the conversion of 8.1V~12.6V voltage from 3 series 2 parallel lithium battery packs to 10V~200V stepless adjustable power supply voltage, and the power supply voltage ripple is as low as mV level. It can provide a wide range of bias voltage power supply for most SAPDs, and realize the switching of SAPD between linear mode and Geiger mode.

[0017] 2. Automatic scanning of the full operating voltage range for SAPD: The FPGA chip controls the digital positioner to perform voltage adjustment scanning of the SAPD from 10V to 200V, and the start voltage, end voltage, and voltage adjustment step size can be set.

[0018] 3. Automatic selection of amplification gain in linear region sampling mode: The scheme of using a transimpedance amplifier circuit in series with a programmable amplifier circuit to sample weak currents in the SAPD in the linear region, and the FPGA chip on the processing board can automatically select the amplification gain by controlling the channel selector of the programmable amplifier circuit.

[0019] 4. Stepless adjustment of sampling sensitivity to single-photon avalanche voltage pulses in Geiger sampling mode: Using an amplifier-comparison-digital converter (ADC), when a weak avalanche voltage pulse signal is generated on the SAPD in the Geiger region, the circuit amplifies and filters it before outputting it to the FPGA chip on the processing board for pulse counting. The FPGA chip can control the ADC chip to adjust the sampling circuit's sensitivity to the avalanche voltage pulse signal. Through the coordinated filtering of hardware circuitry and software algorithms, the pulse noise suppression rate reaches over 90% under no-light conditions.

[0020] 5. In Geiger sampling mode, active or passive quenching of the SAPD can be achieved through a selection circuit. Using a passive quenching resistor connected in parallel with an active quenching circuit, when the system is in Geiger sampling mode, the processing board module can select to enable either the active or passive quenching circuit to quench the SAPD, resulting in high efficiency and applicability to various scenarios. Attached Figure Description

[0021] Figure 1 A schematic diagram of a weak current and avalanche voltage pulse sampling system architecture for SAPD; Figure 2 A schematic diagram of a weak current and avalanche voltage pulse sampling system for SAPD; Figure 3 This is a schematic diagram of a non-isolated Flyback circuit. Figure 4 This is a schematic diagram of a high-voltage LDO circuit; Figure 5 This is a schematic diagram of a linear sampling processing circuit; Figure 6 This is a schematic diagram of the Geiger sampling processing circuit; Figure 7 A schematic diagram of a passive quenching resistor connected in parallel with an active quenching circuit; Figure 8 This is a diagram of the output signal of the linear sampling processing circuit when the SAPD is operating in the linear region. Detailed Implementation

[0022] The present invention will be further explained below with reference to the accompanying drawings; like Figure 1 As shown, a weak current and avalanche voltage pulse sampling system for SAPD includes a power supply module, a detection and sampling module, and a control and processing module.

[0023] like Figure 2 As shown, the overall system structure adopts a modular design. The external structure consists of front and rear covers, a two-piece hatch cover, and a base, forming a complete protective frame. The internal structure integrates components such as raised columns, interface boards, and development board mounting bases. Through optimized layout based on structural mechanics, the system can effectively ensure safety and stability during operation.

[0024] The power module is a 3-series, 2-parallel 18650 lithium battery pack, providing an operating voltage of 8.1V~12.6V for the detection and sampling module and the control processing module. The power module has a DC-05 female input terminal, which can be connected to an AC power source via a power adapter to charge the lithium battery pack or directly power the detection and sampling module and the control processing module.

[0025] The detection and sampling module includes a reverse connection protection circuit, a voltage conversion circuit, an SAPD sensor, a mode conversion circuit, a linear sampling processing circuit, and a Geiger sampling processing circuit. The voltage conversion circuit is connected to the output of the power supply module via the reverse connection protection circuit, converting the power supply module's output voltage into different operating voltages to power the SAPD sensor, the linear sampling processing circuit, and the Geiger sampling processing circuit. The mode conversion circuit switches the connection between the SAPD sensor and either the linear or Geiger sampling processing circuit according to instructions from the control processing module. The linear and Geiger sampling processing circuits receive the output signal from the SAPD sensor, process it, and return the processed signal to the control processing module.

[0026] The reverse connection protection circuit consists of a diode and a fuse. When the circuit is reversed, the fuse and diode will cut off the circuit to prevent the reverse voltage from continuing to supply power to the circuit.

[0027] The voltage conversion circuit includes an 8.1V~12.6V to +5V power supply circuit, an 8.1V~12.6V to -5V power supply circuit, an 8.1V~12.6V to 3.3V power supply circuit, an 8.1V~12.6V to 220V power supply circuit, and a high-voltage LDO circuit, which can provide multiple power supply outputs of 220V, 20V~180V, ±5V, and 3.3V.

[0028] The 8.1V~12.6V to +5V power supply circuit adopts a DC-DC converter in series with an LDO (low dropout linear regulator) circuit. The DC-DC circuit uses a BUCK-type voltage drop circuit to reduce the output voltage of the power module to 7.5V, and then the LDO circuit further reduces the +7.5V voltage to +5V. The 8.1V~12.6V to +5V power supply circuit has an output capability of 5V / 1A and an output voltage ripple as low as mV, greatly filtering out noise generated by the external power adapter or DC-DC circuit.

[0029] The 8.1V~12.6V to 3.3V power supply circuit is similar to the 8.1V~12.6V to +5V power supply circuit. First, a BUCK-type step-down circuit reduces the output voltage of the power module to +4.5V, and then an LDO circuit further reduces the +4.5V voltage to +3.3V. The output capability of the 8.1V~12.6V to 3.3V power supply circuit reaches the 3.3V / 1A level.

[0030] The 8.1V~12.6V to -5V power supply circuit adopts a DC-DC series LDO circuit scheme. First, the voltage output by the power module is reduced to -6.0V through an inverting buck-boost circuit, and then the LDO circuit further reduces the -6.0V voltage to -5.0V. The output capability of the 8.1V~12.6V to -5V power supply circuit reaches the -5.0V / 0.1A level.

[0031] The 8.1V~12.6V to 220V power supply circuit adopts the following... Figure 3 The non-isolated Flyback circuit topology shown increases the output voltage of the power module to 220V.

[0032] The high-voltage LDO circuit uses, for example Figure 4 The high-voltage output adjustable LDO scheme shown uses a 256-bit precision digital positioner AD5272BRMZ-50 as the feedback resistor, powered by an 8.1V~12.6V to 3.3V power supply circuit. It communicates with the control processing module through the IIC communication protocol, adjusts the resistance value, and outputs a voltage of 20~180V.

[0033] The SAPD sensor is a silicon carbide avalanche photodiode, which is plugged into the detection and sampling module via a TO-18 package. The negative terminal of the SAPD sensor is connected to the output of the high-voltage LDO circuit, and the positive terminal is connected to either the linear sampling processing circuit or the Geiger sampling processing circuit via a mode conversion circuit. The SAPD sensor can switch between linear mode and Geiger mode depending on the output voltage of the high-voltage LDO circuit.

[0034] The mode conversion circuit is a single-pole double-throw magnetic latching relay driven by an NMOS circuit, powered by an 8.1V~12.6V to +5V power supply circuit. The control terminal of the NMOS circuit is connected to the control processing module, and drives the single-pole double-throw magnetic latching relay according to the instructions of the control processing module, changing the connection relationship between the SAPD sensor and the linear sampling processing circuit and the Geiger sampling processing circuit.

[0035] When the SAPD sensor operates in linear mode, its output photocurrent is very weak, requiring current-to-voltage conversion and amplification via circuitry. For example... Figure 5As shown, the linear sampling processing circuit employs a two-stage amplification scheme. The first stage uses a transimpedance amplifier circuit to convert the weak photocurrent output from the positive electrode of the SAPD sensor into a voltage, which is then amplified by an amplifying resistor. Compared to the feedback integration method and the sampling resistor method, the transimpedance amplification method not only has higher detection accuracy but also avoids integral voltage drift, making it well-suited for the signal processing requirements of the SAPD sensor in linear mode. The second stage uses a multiplexer and operational amplifier circuit. A multiplexer U26 is connected in parallel with an inverting proportional amplifier circuit. The control terminals A0, A1, A2, and EN of the multiplexer U26 are connected to the control processing module. Based on the instructions from the control processing module, different resistance levels are selected to change the amplification factor of the inverting proportional amplifier circuit, thus amplifying the voltage output from the transimpedance amplifier circuit a second time. This voltage is then transmitted to the control processing module through the output port of the operational amplifier U28. By configuring resistors R157~R159, R161, R163, and R165~R167, the amplification factor of the inverting proportional amplifier circuit can be designed to be 1x, 1.5x, 2x, 5x, 8x, 10x, or 15x. Operational amplifiers U27 and U28 are dual-powered by an 8.1V~12.6V to +5V power supply circuit and an 8.1V~12.6V to -5V power supply circuit.

[0036] Under extremely high bias voltages, the SAPD sensor operates in Geiger mode and outputs avalanche pulses. After sampling, the SAPD sensor in the activated state requires current quenching and device reset. This includes active and passive quenching methods. Active quenching refers to the process of rapidly suppressing the avalanche current through external circuitry after the SAPD sensor experiences an avalanche multiplication effect, restoring the SPAD to its initial state. Passive quenching, on the other hand, utilizes the inherent characteristics of the SAPD sensor or passive quenching resistors to quench the avalanche current and reset the SPAD sensor.

[0037] The Geiger sampling processing circuit includes a DAC circuit, an amplifier circuit, a comparator circuit, an active quenching circuit, and a passive quenching resistor. For example... Figure 6 As shown, the avalanche voltage pulse signal output from the positive terminal of the SAPD sensor is first amplified by the amplifier circuit composed of operational amplifier U29, and then input to the non-inverting input of comparator U30. The inverting input of comparator U30 is connected to the output of the DAC circuit, which compares the amplified avalanche pulse signal with a reference voltage and outputs the comparison result to the control processing module. The DAC circuit uses a 16-bit high-precision DAC chip and communicates with the control processing module through the IIC communication protocol. According to the instructions of the control processing module, the output voltage of the DAC chip is adjusted to provide an adjustable reference voltage within the range of 0V to 2V for the comparator circuit, thereby adjusting the sensitivity of the Geiger sampling processing circuit to sample the avalanche pulse signal output by the SPAD sensor. Figure 7 As shown, the active quenching circuit consists of a low-side NMOS transistor and a high-side PMOS transistor. The low-side NMOS transistor Q6 drives the high-side PMOS transistor Q8. When avalanche multiplication occurs in the SPAD sensor, the avalanche voltage pulse signal output from the positive terminal of the SPAD sensor passes through an amplifier circuit and a comparator circuit. The output signal drives the MOS transistors in the active quenching circuit, thereby driving the high-side PMOS transistor Q8 to discharge the anode voltage of the SPAD, achieving active quenching of the SPAD. The passive quenching resistor is a 10KΩ resistor R212 connected to the anode of the SPAD sensor. After avalanche multiplication occurs in the SPAD sensor, passive quenching is automatically achieved through the passive quenching resistor.

[0038] The control processing module uses an FPGA as the control chip, powered by an 8.1V~12.6V to +5V power supply circuit. It communicates with the detection and sampling module via I / O interfaces to switch the operating mode of the SAPD sensor and read the sampling signal. It also has multiple communication interfaces, allowing it to communicate with a host computer, receive control commands from the host computer, and send sampling information back to the host computer.

[0039] This sampling system can detect and acquire weak current and avalanche voltage pulses from SAPD sensors in linear and Geiger modes. After amplification and filtering, the pulse waveform read by the control processing module is as follows: Figure 8 As shown. In linear mode, this system can detect the weakest current signal level of 10nA, with an adjustable gain range of 6dB to 40dB and an output signal ripple of less than 10mV. In Geiger mode, this system can detect the weakest voltage signal level of 10mV, with an adjustable gain range of 6dB to 30dB and an output signal ripple of less than 10mV. Therefore, this application can effectively detect the photoelectric signal output by the SAPD sensor and achieve weak current sampling.

Claims

1. A weak current and avalanche voltage pulse sampling system for SAPD, comprising a power supply module, a detection and sampling module, and a control and processing module, wherein the power supply module provides operating voltage to the detection and sampling module and the control and processing module, the detection and sampling module includes a voltage conversion circuit for converting the output voltage of the power supply module into different operating voltages, an SAPD sensor, and a sampling and processing circuit for sampling the output of the SAPD sensor and transmitting it to the control and processing module, the control and processing module being used to receive the sampling signal output by the sampling and processing circuit and transmit the sampling information back to a host computer; characterized in that: The detection sampling module further includes a mode conversion circuit, and the sampling processing circuit includes a linear sampling processing circuit and a Geiger sampling processing circuit. The voltage conversion circuit provides different bias voltages to the SAPD sensor according to the instructions of the control processing module, switching the SAPD sensor to operate in linear mode or Geiger mode. The mode conversion circuit switches the connection between the SAPD sensor and the linear sampling processing circuit or the Geiger sampling processing circuit according to the instructions of the control processing module. The linear sampling processing circuit is used to convert the current output from the positive terminal of the SAPD sensor into a voltage signal and amplify it. The Geiger sampling processing circuit is used to compare the magnitude of the positive terminal output signal of the SAPD sensor with the reference voltage and drive the quenching circuit to quench the current and reset the device of the SAPD sensor in the excited state. The control processing module receives control commands from the host computer, communicates with the detection and sampling module, and switches the working mode of the SAPD sensor.

2. The weak current and avalanche voltage pulse sampling system for SAPD as described in claim 1, characterized in that: The control processing module also includes a hardware noise reduction module.

3. The weak current and avalanche voltage pulse sampling system for SAPD as described in claim 2, characterized in that: The hardware noise reduction module uses a combination of RC low-pass filtering and second-order active filtering to filter out high-frequency glitches in the sampling signal output by the sampling processing circuit, and uses a Schmitt trigger to set a hysteresis threshold to shape the signal, combined with a monostable trigger to identify the pulse width.

4. The weak current and avalanche voltage pulse sampling system for SAPD as described in claim 1, characterized in that: By using a baseline detection dynamic threshold algorithm, combined with median filtering and pulse correlation detection, isolated noise pulses in the sampling information returned by the control processing module are eliminated. Kalman filtering is then used to establish a signal state model to predict and correct noise interference.

5. The weak current and avalanche voltage pulse sampling system for SAPD as described in claim 1, characterized in that: In linear mode, the voltage conversion circuit provides a bias voltage less than the avalanche voltage to the SAPD sensor under the control of the control processing module, and samples the weak photocurrent signal output by the SAPD sensor through the linear sampling processing circuit. In Geiger mode, the voltage conversion circuit provides a bias voltage greater than the avalanche voltage to the SAPD sensor under the control of the control processing module, and samples the weak avalanche voltage pulse signal output by the SAPD sensor through the Geiger sampling processing circuit.

6. The weak current and avalanche voltage pulse sampling system for SAPD as described in claim 1 or 5, characterized in that: The voltage conversion circuit includes an 8.1V~12.6V to +5V power supply circuit, an 8.1V~12.6V to -5V power supply circuit, an 8.1V~12.6V to 3.3V power supply circuit, an 8.1V~12.6V to 220V power supply circuit, and a high-voltage LDO circuit, providing multiple power supply outputs of 220V, 20V~180V, ±5V, and 3.3V.

7. The weak current and avalanche voltage pulse sampling system for SAPD as described in claim 6, characterized in that: The high-voltage LDO circuit adopts a high-voltage output adjustable LDO scheme, uses a digital positioner as a feedback resistor, and communicates with the control processing module through the IIC communication protocol to adjust the resistance value of the digital positioner and output a voltage that varies from 20 to 180V. The output section of the high-voltage LDO circuit is connected to the negative terminal of the SAPD sensor to provide a bias voltage for the SAPD sensor.

8. The weak current and avalanche voltage pulse sampling system for SAPD as described in claim 1, characterized in that: The linear sampling processing circuit adopts a two-stage amplification scheme. The first stage amplification uses a transimpedance amplifier circuit to convert the current signal output from the positive terminal of the SAPD sensor into a voltage signal and amplify it. The second-stage amplification uses an inverting proportional amplifier circuit connected in parallel with a multiplexer. The control terminal of the multiplexer is connected to the control processing module. According to the instructions of the control processing module, different resistance levels are selected to change the amplification factor of the inverting proportional amplifier circuit. The output terminal of the inverting proportional amplifier circuit is connected to the control processing module.

9. The weak current and avalanche voltage pulse sampling system for SAPD as described in claim 8, characterized in that: The amplification factor of the inverting proportional amplifier circuit can be controlled by a multiplexer to be 1x, 1.5x, 2x, 5x, 8x, 10x, or 15x.

10. The weak current and avalanche voltage pulse sampling system for SAPD as described in claim 1, characterized in that: The Geiger sampling processing circuit includes a DAC circuit, an amplifier circuit, a comparator circuit, an active quenching circuit, and a passive quenching resistor. The amplifier circuit amplifies the avalanche voltage pulse signal output from the positive terminal of the SAPD sensor and then inputs it to the comparison terminal of the comparator circuit. The reference voltage terminal of the comparator circuit is connected to the output of the DAC circuit, compares the amplified avalanche pulse signal with the reference voltage, and outputs the comparison result to the control processing module. The DAC circuit adjusts the output voltage of the DAC chip according to the instructions of the control processing module, providing an adjustable reference voltage for the comparator circuit. The active quenching circuit consists of a low-side NMOS transistor and a high-side PMOS transistor. The low-side NMOS transistor Q6 is responsible for driving the high-side PMOS transistor. When avalanche multiplication occurs in the SPAD sensor, the avalanche voltage pulse signal output from the positive electrode of the SPAD sensor passes through an amplifier circuit and a comparator circuit. The output signal drives the MOS transistor of the active quenching circuit, thereby driving the high-side PMOS transistor of the active quenching circuit to discharge the anode voltage of the SPAD, thus realizing the active quenching of the SPAD. The passive quenching resistor is connected to the anode resistor of the SAPD sensor. After the SAPD sensor experiences avalanche multiplication, passive quenching is automatically achieved through the passive quenching resistor.

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