An amplifier circuit for pulse current signals and its working method

Abstract

A pulse current signal amplification circuit and its operating method are disclosed, comprising an APD module, a transimpedance amplifier module, an AC coupling module, and a reverse current cancellation module. The APD module is connected to the AC coupling module, the AC coupling module is connected to the transimpedance amplifier module, and the reverse current cancellation module is connected to the input and output terminals of the transimpedance amplifier module as its input terminals. To ensure that the DC bias voltage at the signal input terminal of the APD is adjustable and does not interfere with the DC bias voltage of the receiving circuit, AC coupling is used at the input. When a large signal is input, the AC coupling capacitor charges; after the signal ends, the AC coupling capacitor discharges, generating a reverse current that affects the circuit's operating state. This invention accelerates the recovery of the circuit from abnormal operating states. The reverse current cancellation circuit of this invention is configured to open an internal current path to compensate for the reverse current when the output potential of the transimpedance amplifier module is lower than that at the input terminal, thereby reducing the reverse current flowing through the transimpedance amplifier module and thus reducing the potential change at the output terminal of the transimpedance amplifier module.

Description

Technical Field

[0001] This invention belongs to the field of electronic circuit design technology, specifically relating to an amplifier circuit for pulse current signals and its operating method. Background Technology

[0002] LiDAR (Light Detection and Ranging) is a sensing device that emits laser signals of a specific wavelength onto the surface of an object and uses the reflected signals to obtain distance information. Compared with ordinary microwave radar, LiDAR has advantages such as high resolution, good concealment, strong anti-interference ability, small size, and light weight. Among them, a time-of-flight (TOF) ranging scheme that uses a pulsed laser as the transmitter is currently widely researched and applied. In this scheme, the corresponding receiver measures the distance based on the time of the transmitted signal and the time of the received echo pulse.

[0003] In lidar systems employing avalanche photodiodes (APDs) as the receiver, the anode of the APD array is connected to a negative potential, as low as -100V or even lower. The APD cathode is connected to the receiver circuit input, with the potential established by the internal loop of the circuit. When using a voltage-parallel negative feedback transimpedance amplifier, the receiver input is typically between the power supply voltage and ground potential to achieve optimal output swing and gain performance. In this case, the voltage drop across each APD in the entire array is uniform. However, in reality, variations can occur during the manufacturing process or other processes, leading to differences in the responsivity of different APDs at the same voltage drop. In such cases, it is necessary to adjust the voltage drop across the APD to achieve a responsivity that is as consistent as possible. However, for negative potentials, small-amplitude adjustments are often impossible due to the extremely low voltage. Therefore, the circuit employs an AC-coupled input mode to isolate the DC potential of the APD cathode and the TIA input, enabling APD cathode potential adjustment without affecting the internal operating potential of the TIA. The receiver circuit input uses AC coupling. Because the optical pulse signal of the echo pulse is strong, the lower edge of the electrical signal will continue to drop after recovering to the static operating potential until it drops to a certain potential and then slowly recovers to the static operating potential. During this process, the circuit is in an abnormal working state. If this process has not ended when the next echo pulse signal arrives, it will affect the processing of the next echo pulse signal and cause measurement errors. Summary of the Invention

[0004] The purpose of this invention is to provide an amplification circuit for pulse current signals and its operating method, which accelerates the recovery of the circuit from abnormal operating conditions, thereby solving the problem that slow potential recovery affects the processing of the next echo pulse signal and leads to measurement errors.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An amplification circuit for pulse current signals includes an APD module, a transimpedance amplifier module, an AC coupling module, and a reverse current cancellation module; the APD module is connected to the AC coupling module, the AC coupling module is connected to the transimpedance amplifier module, and the reverse current cancellation module is connected to the input and output terminals of the transimpedance amplifier module as an input terminal.

[0007] The APD module is used to convert optical signals into pulsed current signals; the AC coupling module is used to transmit signal current to the transimpedance amplifier module while isolating DC potential and current; the transimpedance amplifier module is used to convert current signals into voltage signals; and the reverse current cancellation module is used to establish a recovery channel when reverse current arrives.

[0008] Furthermore, the transimpedance amplifier module includes: a single-ended input single-ended output amplifier and a feedback resistor, which is connected in parallel across the input and output terminals of the single-ended input single-ended output amplifier.

[0009] Furthermore, the AC coupling module is a coupling capacitor, which is placed between the APD module and the transimpedance amplifier module, and the capacitance value is within a preset capacitance range.

[0010] Furthermore, the APD module is an APD coupled to the internal cathode of the circuit.

[0011] Furthermore, the reverse current elimination module includes a filter module, a differential input single-ended output amplifier module, and a reverse current compensation NMOS transistor; the output terminals of the two filter modules are respectively connected to the positive and negative input terminals of the differential input single-ended output amplifier module, the input terminals of the two filter modules are respectively connected to the two ends of the transimpedance amplifier module, and the output terminal of the differential input single-ended output amplifier module is connected to the gate terminal of the reverse current compensation NMOS transistor.

[0012] Furthermore, the input terminal of the filter module corresponding to the positive input terminal of the differential input single-ended output amplifier module is connected to the output terminal of the transimpedance amplifier module, and the input terminal of the filter module corresponding to the negative input terminal of the differential input single-ended output amplifier module is connected to the input terminal of the transimpedance amplifier module.

[0013] Furthermore, the filtering module includes a filter resistor and a filter capacitor, with one end of the filter resistor and the filter capacitor connected in series and the other end of the filter capacitor grounded.

[0014] Furthermore, the gate of the NMOS transistor used for compensating reverse current is connected to the output of the differential input single-ended output amplifier module, the source is grounded, and the drain is connected to the input of the transimpedance amplifier module.

[0015] Furthermore, a method for amplifying a pulse current signal using an amplification circuit includes the following steps:

[0016] The AC coupling module is configured to transmit the AC component in the signal to the input terminal of the transimpedance amplifier module; the transimpedance amplifier module is configured to convert the current signal into a voltage signal; the reverse current cancellation circuit is configured to open the internal current path to compensate for the reverse current when the output terminal potential of the transimpedance amplifier module is lower than that of the input terminal, thereby reducing the reverse current flowing through the transimpedance amplifier module and thus reducing the output terminal potential change of the transimpedance amplifier module.

[0017] The NMOS transistor NM, which compensates for reverse current, provides a current path for reverse current. When the output potential of the transimpedance amplifier module is lower than the input potential of the transimpedance amplifier module, the relatively low-frequency signal is transmitted to the differential input terminal of the differential input single-ended output amplifier after passing through the filter circuit. The amplifier then amplifies the signal and outputs the corresponding level to the gate terminal of the NMOS transistor NM to control the magnitude of its compensation current.

[0018] Compared with the prior art, the present invention has the following technical effects:

[0019] The reverse current cancellation circuit of this invention utilizes the property that the reverse current is opposite in direction to the signal current for detection. Specifically, when the signal current arrives, the output potential of the transimpedance amplifier module is higher than the input potential, while when the reverse current arrives, the output current of the transimpedance amplifier module is lower than the input potential. When the potential change caused by the reverse current occurs, the reverse current cancellation loop detects this state and turns on the NMOS transistor providing the reverse current. Thereafter, the reverse current no longer flows through the transimpedance amplifier but through the NMOS transistor until the output potential returns to the preset DC potential. At this point, the capacitor discharge process ends, and no more reverse current is generated.

[0020] The reverse current cancellation circuit of this invention is configured to open an internal current path to compensate for reverse current when the output potential of the transimpedance amplifier module is lower than that of the input potential, thereby reducing the reverse current flowing through the transimpedance amplifier module and thus reducing the potential change at the output of the transimpedance amplifier module. When the output potential of the transimpedance amplifier module is lower than that of the input potential, a relatively low-frequency signal is transmitted to the differential input terminal of the differential input single-ended output amplifier through a filter circuit. After amplification, the amplifier outputs the corresponding level to the gate terminal of the NM compensation reverse current NMOS transistor to control the magnitude of its compensation current. Attached Figure Description

[0021] Figure 1 The diagram shown is a schematic diagram of a pulse current signal amplification circuit with reverse current elimination function provided in an embodiment of the present invention.

[0022] Component labeling: 01 AC coupling module, 02 transimpedance amplifier module, 03 reverse current elimination module, 04 APD module.

[0023] Figure 2 The diagram shown illustrates the input signal processing procedure of this invention.

[0024] Figure 3 The diagram shows the reverse current processing procedure after the signal ends according to the present invention.

[0025] Figure 4 The diagram shows the waveforms output by pulse current signal amplifier circuits using the present invention and those not using the present invention after processing a large pulse current input. The dashed line represents the output waveform of the pulse current signal amplifier circuit without the present invention, and the solid line represents the output waveform using the present invention. Detailed Implementation

[0026] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0027] The following is combined with Figure 1 The following is an exemplary description of the pulse current signal amplification circuit provided in the embodiments of this disclosure.

[0028] This disclosure provides a pulse current signal amplification circuit, which includes: an APD module, an AC coupling module, a transimpedance amplifier module, and a reverse current cancellation module;

[0029] The APD module converts optical signals into pulsed current signals.

[0030] The AC coupling module provides a series capacitor to isolate the input DC level and DC current from the internal circuit, thus avoiding affecting the circuit's operating state.

[0031] The transimpedance amplifier module converts the current pulse signal into a voltage pulse signal and amplifies it by a preset factor.

[0032] The reverse current elimination circuit obtains the gate potential of the compensation reverse current NMOS transistor by comparing the potentials of the input and output terminals of the transimpedance amplifier module after passing through the filter module. The compensation reverse current NMOS transistor generates a corresponding current to compensate for the reverse current, thereby accelerating the discharge process of the AC coupling capacitor.

[0033] Specifically, the capacitance and resistance values ​​of the capacitors and resistors in the filter circuit are within a preset range.

[0034] Specifically, the reverse current is due to the presence of the AC coupling module, which causes the AC coupling module to discharge after being fully charged by the signal when a large input pulse current signal passes through, thereby generating the reverse current.

[0035] Specifically, the transimpedance amplifier module and the reverse current elimination module also include a power supply terminal and a ground terminal, wherein the power supply terminal is connected to the supply voltage and the ground terminal is connected to the signal ground.

[0036] Optionally, in the reverse current cancellation module, the attribute of the MOS transistor for compensating reverse current is changed to a PMOS transistor when the input current signal is input in different directions. Correspondingly, the input terminals of the differential input single-ended output amplifier module are also swapped.

[0037] This disclosure provides a pulse current signal amplification circuit, comprising: an AC coupling module 01, a transimpedance amplifier module 02, a reverse current cancellation module 03, and an APD module 04; the anode of the APD module 04 is connected to an externally supplied negative potential, and the cathode is connected to the input terminal of the AC coupling module 01; the output terminal of the AC coupling module 01 is connected to the input terminal of the transimpedance amplifier module 02; the output terminal of the transimpedance amplifier module 02 is connected to the output terminal of the overall circuit; the positive input terminal of the reverse current cancellation module 03 is connected to the output terminal of the transimpedance amplifier module 02, the negative input terminal is connected to the input terminal of the transimpedance amplifier module 02, and the output terminal is connected to the input terminal of the transimpedance amplifier module 02; wherein the AC coupling module 01 is configured to transmit the AC component in the signal to the input terminal of the transimpedance amplifier module 02; the transimpedance amplifier module 02 is configured to convert the current signal into a voltage signal; the reverse current cancellation circuit 03 is configured to open an internal current path to compensate for the reverse current when it detects that the output terminal potential of the transimpedance amplifier module 02 is lower than that of the input terminal, thereby reducing the reverse current flowing through the transimpedance amplifier module 02 and thus reducing the potential change at the output terminal of the transimpedance amplifier module 02.

[0038] The reverse current cancellation circuit 03 includes: a differential input single-ended output amplifier 031, filter circuits 032 and 033, and a reverse current compensation NMOS transistor NM; the filter circuits 032 and 033 are respectively composed of resistor R1 and capacitor C1 and resistor R2 and capacitor C2, respectively. One end of each of resistors R1 and R2 serves as the input terminal of filter circuits 032 and 033, and the other end serves as the output terminal of filter circuits 032 and 033, respectively. One end of each of capacitors C1 and C2 is connected to the output terminal of filter circuits 032 and 033, respectively, and the other end is grounded. Input terminal 32, which is the positive input terminal of the entire reverse current cancellation circuit 03, is connected to the output terminal of the transimpedance amplifier module 02. Input terminal 033, which is the negative input terminal of the entire reverse current cancellation circuit 03, is connected to the input terminal of the transimpedance amplifier module 02. The positive input terminal of the differential input single-ended output amplifier 031 is connected to the output terminal of the filter circuit 032, the negative input terminal is connected to the output terminal of the filter circuit 033, and the output terminal is connected to the gate terminal of the compensation reverse current NMOS transistor NM. The drain terminal of the compensation reverse current NMOS transistor NM is connected to the input terminal of the transimpedance amplifier module 02, and the source terminal is connected to ground.

[0039] The NMOS transistor NM that compensates for reverse current provides a current path for reverse current. When the output potential of the transimpedance amplifier module 02 is lower than the input potential of the transimpedance amplifier module 02, the relatively low frequency signal is transmitted to the differential input terminal of the differential input single-ended output amplifier 031 through the filter circuits 032 and 033. After amplification, the amplifier outputs the corresponding level to the gate terminal of the NMOS transistor NM that compensates for reverse current to control the magnitude of its compensation current.

[0040] The resistance and capacitance values ​​of resistor R1 and capacitor C1 and resistor R2 and capacitor C2 in the filter circuits 032 and 033 are within a preset range.

[0041] The AC coupling module includes a coupling capacitor; the capacitance value of the capacitor is within a preset capacitance range; the AC coupling module is used to transmit the signal current to the transimpedance amplifier module while isolating the DC potential and the current, and the corresponding input terminal can also be set with the required DC potential without affecting the internal circuit operation.

[0042] The transimpedance amplifier module 02 completes the current-to-voltage conversion. The overall module gain is RF. The relationship between the output voltage TIA_OUT generated at the output terminal and the input current TIA_IN at the input terminal is TIA_OUT = TIA_IN * RF.

[0043] The pulse current amplifier circuit outputs a voltage such that, after a large current signal is input, the voltage is... Figure 4 The black curve in the middle is shown. As can be seen from the graph, compared to... Figure 4 The dashed line indicates a pulse current amplifier circuit that does not employ this invention. The solid line represents the output of the circuit using this invention, which recovers to its initial potential after a detection period. The pulse current amplifier without this invention, however, has a longer recovery time, which could cause the circuit to operate out of its optimal position if the next signal arrives during this period. In the signal transmission section, the output results of the pulse current amplifiers using and without this invention are completely identical, indicating that this invention does not affect the signal transmission process.

[0044] In summary, the present invention provides an amplification circuit and its operating method for pulse current signals. By establishing a detection loop and a discharge path, the reverse current flows to the discharge path instead of flowing through the transresistance, thus solving the problem of slow recovery of the operating potential caused by the reverse current generated after the signal ends when a large current pulse signal is input into a conventional pulse current amplification circuit.

Claims

1. An amplifier circuit for pulse current signals, characterized in that, It includes an APD module, a transimpedance amplifier module, an AC coupling module, and a reverse current elimination module; the APD module is connected to the AC coupling module, the AC coupling module is connected to the transimpedance amplifier module, and the reverse current elimination module is connected to the input and output terminals of the transimpedance amplifier module as input terminals; The APD module is used to convert optical signals into pulsed current signals; the AC coupling module is used to transmit signal current to the transimpedance amplifier module while isolating DC potential and current. The transimpedance amplifier module is used to convert current signals into voltage signals; the reverse current cancellation module is used to establish a recovery path when reverse current arrives. The reverse current elimination module includes a filter module, a differential input single-ended output amplifier module, and a reverse current compensation NMOS transistor. The output terminals of the two filter modules are respectively connected to the positive and negative input terminals of the differential input single-ended output amplifier module, and the input terminals of the two filter modules are respectively connected to the two ends of the transimpedance amplifier module. The output terminal of the differential input single-ended output amplifier module is connected to the gate terminal of the reverse current compensation NMOS transistor. The input terminal of the filter module corresponding to the positive input terminal of the differential input single-ended output amplifier module is connected to the output terminal of the transimpedance amplifier module, and the input terminal of the filter module corresponding to the negative input terminal of the differential input single-ended output amplifier module is connected to the input terminal of the transimpedance amplifier module.

2. The amplification circuit for pulse current signals according to claim 1, characterized in that, The transimpedance amplifier module includes a single-ended input single-ended output amplifier and a feedback resistor, which is connected in parallel across the input and output terminals of the single-ended input single-ended output amplifier.

3. The amplification circuit for pulse current signals according to claim 1, characterized in that, The AC coupling module is a coupling capacitor, which is placed between the APD module and the transimpedance amplifier module. The capacitance value is within a preset range.

4. The amplification circuit for pulse current signals according to claim 1, characterized in that, The APD module is an APD that is coupled to the internal cathode of the circuit.

5. The amplification circuit for pulse current signals according to claim 1, characterized in that, The filtering module includes a filter resistor and a filter capacitor. One end of the filter resistor and the filter capacitor are connected in series, and the other end of the filter capacitor is grounded.

6. The amplification circuit for pulse current signals according to claim 1, characterized in that, The gate of the NMOS transistor used for reverse current compensation is connected to the output of the differential input single-ended output amplifier module, the source is grounded, and the drain is connected to the input of the transimpedance amplifier module.

7. A method for operating a pulse current signal amplification circuit, characterized in that, The amplification circuit based on the pulse current signal according to any one of claims 1 to 6 includes the following steps: The AC coupling module is configured to transmit the AC component in the signal to the input terminal of the transimpedance amplifier module; the transimpedance amplifier module is configured to convert the current signal into a voltage signal; the reverse current cancellation circuit is configured to open the internal current path to compensate for the reverse current when it detects that the output potential of the transimpedance amplifier module is lower than that of the input terminal, thereby reducing the reverse current flowing through the transimpedance amplifier module and thus reducing the output potential change of the transimpedance amplifier module. The NMOS transistor NM, which compensates for reverse current, provides a current path for reverse current. When the output potential of the transimpedance amplifier module is lower than the input potential of the transimpedance amplifier module, the relatively low-frequency signal is transmitted to the differential input terminal of the differential input single-ended output amplifier after passing through the filter circuit. The amplifier then amplifies the signal and outputs the corresponding level to the gate terminal of the NMOS transistor NM to control the magnitude of its compensation current.

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