A current-compensated transimpedance amplification circuit

Abstract

The application discloses a kind of compensation current adjustable transimpedance amplification circuit, including reference voltage circuit, bipolar direct current circuit, voltage-current conversion circuit and transimpedance amplification circuit.First, reference voltage circuit generates high-precision, low-noise reference voltage, then through bipolar direct current circuit, it is converted into certain voltage within positive and negative reference voltage by reference voltage, and the voltage also has the characteristics of high-precision low-noise, then the voltage is converted into compensation current by voltage-current conversion circuit, and finally, through transimpedance amplification circuit, the AC component is converted into voltage signal output by offsetting direct current component.The application can realize high-precision current compensation, and has the characteristics of low noise.The circuit of the application can be used in inertial measurement device, magnetometer and other precision optoelectronic measurement fields.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection, and more particularly to a transimpedance amplifier circuit with adjustable compensation current. Technical Background

[0002] A transimpedance amplifier is a front-end amplifier for current-output sensors (such as photodiodes), used to convert the sensor's output current into a voltage signal. The transimpedance amplifier converts the input I into an output voltage V = IR through a feedback resistor R connected across the negative input and output of an operational amplifier. SERF (Spin-Exchange-Relaxation-Free) quantum systems exhibit high sensitivity to extremely weak magnetic environments, thus attracting significant attention in the field of quantum measurement. By utilizing a pump laser system to polarize atoms, the optical rotation angle of the probe light induced by the spin precession of alkali metal-inert gas atoms in an extremely weak magnetic environment is detected, thereby achieving ultra-high sensitivity inertial measurement. A photodiode, as an optical sensor, is used to measure the intensity of the probe light, and then an external transimpedance amplifier converts the probe light power signal into a voltage signal for measurement.

[0003] The photocurrent converted from the probe light consists mainly of two components: a DC component and an AC component. The DC component primarily originates from the dark current of the photodiode, while the AC component comes from the modulation signal generated by the lock-in amplifier. The device measures inertia by detecting the magnitude of the modulation signal. A high DC component significantly limits the AC gain of the transimpedance amplifier. Canceling the DC component can improve the dynamic range of the AC component, thereby improving the measurement accuracy. Currently, the device uses a Thorlabs PDA200C photodiode amplifier, which lacks DC current compensation. Introducing an RC high-pass filter after the photodiode output would affect the bandwidth and closed-loop gain of the entire transimpedance amplifier. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a transimpedance amplifier circuit with adjustable compensation current, which solves the problem that existing technologies are unable to compensate for the large DC component in the photocurrent signal, thus affecting the dynamic range of the AC signal.

[0005] To solve the above problems, the present invention adopts the following technical solution: including a reference voltage circuit, a bipolar DC voltage circuit, a voltage-to-current conversion circuit, and a transimpedance amplifier circuit. The reference voltage circuit converts the power supply voltage into a reference voltage; the bipolar DC voltage circuit converts the reference voltage into positive and negative reference voltages; the voltage-to-current conversion circuit converts the voltage into current; the transimpedance amplifier circuit receives the current signal generated by the voltage-to-current conversion circuit, subtracts it from the current signal flowing into the input port, and converts the subtracted current signal back into a voltage signal for output.

[0006] Furthermore, the reference voltage circuit includes an input capacitor C1, a reference voltage chip U1, and an output capacitor C2; wherein, one end of the capacitor C1 is grounded and the other end is connected to the VIN terminal of the reference voltage chip U1; the GND terminal of the reference voltage chip U1 is grounded; one end of the output capacitor C2 is connected to the VREF terminal of the reference voltage chip U1 and the other end is grounded; the input capacitor C1 filters the power supply voltage; the reference voltage chip U1 converts the power supply voltage into a reference voltage signal; and the output capacitor C2 filters the reference voltage signal.

[0007] Further, the bipolar DC voltage circuit includes a multiplier-type digital-to-analog converter U2, a capacitor C3, resistors R1, R2, and R3, an operational amplifier U3, and an operational amplifier U4; wherein, the VREF terminal of the multiplier-type digital-to-analog converter U2 is connected to the output terminal VREF of the reference voltage chip U1, the GND terminal is grounded, the VDD terminal is connected to the voltage source VDD, the IOUT terminal is connected to the negative input terminal of the operational amplifier U3, and the RFB terminal is connected to the output terminal of the operational amplifier U3; one end of the capacitor C3 is connected to the multiplier-type digital-to-analog converter. The RFB terminal of U2 is connected to the other end of the multiplier-type digital-to-analog converter U2; the positive input terminal of the operational amplifier U3 is grounded and the output terminal is connected to resistor R3; the other end of resistor R3 is connected to the negative input terminal of operational amplifier U4; one end of resistor R1 is connected to the output terminal VREF of the reference voltage chip U1, and the other end of resistor R1 is connected to the negative input terminal of operational amplifier U4; one end of resistor R2 is connected to the negative input terminal of operational amplifier U4, and the other end is connected to the output terminal of operational amplifier U4; the positive input terminal of operational amplifier U4 is grounded.

[0008] The output voltage of the operational amplifier U3 is VDAC = -D / (2 n VREF, where D is the control code of the multiplier-type digital-to-analog converter U2, n is the number of bits in the multiplier-type digital-to-analog converter U2, and VREF is the reference voltage output by the reference voltage chip U1. The output voltage VDAC of the operational amplifier U3 can be changed by adjusting the control code D of the multiplier-type digital-to-analog converter U2.

[0009] The output voltage of the operational amplifier U4 is VCUR = -(R2 / R1 VREF + R2 / R3 VDAC). Taking R1 = R2 = 2R3, we can obtain the output voltage VCUR of the operational amplifier U4 as VCUR = (D / 2 n-1 -1)VREF.

[0010] Further, the voltage-to-current conversion circuit consists of resistors R4, R5, R6, R8, R9, and operational amplifier U5. The voltage-to-current conversion circuit includes resistors R4, R5, R6, R8, R9, and operational amplifier U5; one end of resistor R4 is connected to the negative input terminal of operational amplifier U5, and the other end is connected to the output terminal of operational amplifier U5; one end of resistor R5 is connected to the output terminal of operational amplifier U4, and the other end is connected to the negative input terminal of operational amplifier U5; one end of resistor R6 is connected to the output terminal of operational amplifier U5, and the other end is connected to the negative input terminal of operational amplifier U6; one end of resistor R8 is connected to the bias voltage VBIAS, and the other end is connected to the positive input terminal of operational amplifier U5; one end of resistor R9 is connected to the positive input terminal of operational amplifier U5, and the other end is grounded.

[0011] The output voltage of the operational amplifier U5 is VSHT = R8(R4+R5) / R5(R8+R9)VBIAS-R4 / R5VCUR, where VBIAS is the positive input voltage of the operational amplifier U6.

[0012] The output voltage of the operational amplifier U5 is VSHT = VBIAS - kVCUR; the current flowing through resistor R6 is ISHT = k(1 - D / 2) n-1 VREF / R6;

[0013] Where k = R4 / R5 = R9 / R8, VSHT is the output voltage of operational amplifier U5, VBIAS is the bias voltage of the positive input terminal of operational amplifier U6, D is the control code of multiplier-type digital-to-analog converter U2, and ISHT is the current flowing through resistor R6.

[0014] Furthermore, the current flowing through resistor R6 is ISHT = (VBIAS - kVCUR - VBIAS) / R6. This can be simplified to ISHT = k(1 - D / 2) n-1 VREF / R6.

[0015] Furthermore, the transimpedance amplifier circuit includes a connector P1, a capacitor C4, a resistor R7, and an operational amplifier U6; wherein, the negative input terminal of the connector P1 is grounded; one end of the capacitor C4 is connected to the negative input terminal of the operational amplifier U6, and the other end is connected to the output terminal of the operational amplifier U6; one end of the resistor R7 is connected to the negative input terminal of the operational amplifier U6, and the other end is connected to the output terminal of the operational amplifier U6; the negative input terminal of the operational amplifier U6 is connected to the connector P1, and the positive input terminal is connected to the bias voltage VBIAS;

[0016] The current IBNC input through connector P1 consists of a DC component IDC and an AC component IAC. The output voltage VOUt of operational amplifier U6 is R7(ISHT+IDC+IAC). IDC is eliminated by adjusting ISHT.

[0017] The beneficial effects of this invention are as follows: First, a reference voltage circuit is used to generate a high-precision, low-noise reference voltage. Then, a bipolar DC voltage circuit converts the reference voltage into a voltage within the positive and negative reference voltage range. This voltage also possesses high precision and low noise characteristics. Next, a voltage-to-current conversion circuit converts this voltage into a compensation current. Finally, a transimpedance amplifier circuit cancels out the DC component and converts the AC component into a voltage signal output. This invention can achieve high-precision current compensation and features low noise. It can be easily connected to microcontrollers, DSPs, etc., via the digital interface of a multiplier-type digital-to-analog converter, simplifying control. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the circuit structure of the present invention. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0020] like Figure 1 As shown, the present invention provides a transimpedance amplifier circuit with adjustable compensation current, including a reference voltage circuit, a bipolar DC voltage circuit, a voltage-to-current conversion circuit, and a transimpedance amplifier circuit.

[0021] The reference voltage circuit includes an input capacitor C1, a reference voltage chip U1, and an output capacitor C2. The input capacitor is a 0.1uF ceramic capacitor. Input capacitor C1 is connected to the input terminal VIN of the reference voltage chip U1, used for energy storage and filtering noise from the power supply VCC. The GND terminal of the reference voltage chip U1 is grounded. The output terminal VREF of the reference voltage chip U1 is connected in parallel with the output capacitor C2 to ground, used for energy storage and filtering noise from the reference voltage VREF. The reference voltage chip is model ADR4550, an ultra-low noise, high-precision 5.0V reference voltage source. The output capacitor is a 0.1uF ceramic capacitor.

[0022] The bipolar DC voltage circuit includes a multiplier-type digital-to-analog converter (DAC) U2, capacitor C3, resistors R1, R2, and R3, operational amplifier U3, and operational amplifier U4. The VREF terminal of DAC U2 is connected to the output VREF terminal of the reference voltage chip U1. DAC U2 is connected to the voltage source VDD. One end of capacitor C3 is connected to RFB of DAC U2, and the other end is connected to IOUT of DAC U2. The IOUT terminal of DAC U2 is connected to the negative input terminal of operational amplifier U3, and the positive input terminal of operational amplifier U3 is grounded. The output terminal of operational amplifier U3 is connected to RFB of DAC U2. One end of resistor R1 is connected to the output VREF terminal of the reference voltage chip U1, and the other end is connected to the negative input terminal of operational amplifier U4. One end of resistor R2 is connected to the negative input terminal of operational amplifier U4, and the other end is connected to the output terminal of operational amplifier U4. The positive input terminal of operational amplifier U4 is grounded. The multiplier-type digital-to-analog converter is a DAC7811, a single-channel serial-input multiplier DAC. Resistors R1 and R2 are 10K ohms, 0.1% low-temperature drift surface-mount resistors. Resistor R3 is a 5K ohm, 0.1% low-temperature drift surface-mount resistor. Capacitor C3 is a 10pF ceramic capacitor. Operational amplifiers U3 and U4 are OPA277, dual-channel, 36V, 10μV offset voltage, 0.1μV / ℃ temperature drift, bipolar operational amplifiers.

[0023] The output voltage VCUR of the operational amplifier U4 is (D / 2) n-1 -1)5V, the range is between -5V and 5V.

[0024] The voltage-to-current conversion circuit includes resistors R4, R5, R6, R8, and R9, and operational amplifier U5. One end of resistor R4 is connected to the negative input terminal of operational amplifier U5, and the other end is connected to the output terminal of operational amplifier U5. One end of resistor R5 is connected to the output terminal of operational amplifier U4, and the other end is connected to the negative input terminal of operational amplifier U5. One end of resistor R6 is connected to the output terminal of operational amplifier U5, and the other end is connected to the negative input terminal of operational amplifier U5. One end of resistor R8 is connected to the bias voltage VBIAS, and the other end is connected to the positive input terminal of operational amplifier U5. One end of resistor R9 is connected to the positive input terminal of operational amplifier U5, and the other end is grounded. Resistors R4, R5, R8, and R9 are all 10K ohms, 0.1% low-temperature drift surface-mount resistors. Resistor R6 is a 5M ohm, 0.1% low-temperature drift surface-mount resistor. Operational amplifier U5 is an OPA827, a low-noise, high-precision JFET input operational amplifier.

[0025] The current flowing through resistor R6 is ISHT = (1 - D / 2)n-1 )μA, ranging from -1μA to 1μA.

[0026] The transimpedance amplifier circuit includes connector P1, capacitor C4, resistor R7, and operational amplifier U6. The positive input terminal of connector P1 is connected to the anode of the photodiode, and the negative input terminal of connector P1 is grounded. One end of capacitor C4 is connected to the negative input terminal of operational amplifier U6, and the other end of capacitor C4 is connected to the output terminal of operational amplifier U6. One end of resistor R7 is connected to the negative input terminal of operational amplifier U6, and the other end of resistor R7 is connected to the output terminal of operational amplifier U6. Connector P1 is BNC, capacitor C4 is an 8.2pF ceramic capacitor used for phase compensation, resistor R7 is a 15K ohm, 0.1% low-temperature drift surface mount resistor, and operational amplifier U6 is an ADA4627-1, 36V, 19MHz, low-noise, low-bias-current, JFET operational amplifier.

[0027] Connect the photodiode to this circuit via connector P1. When no modulation signal is introduced into the detection light, adjust the control code through the digital interface of the multiplier-type digital-to-analog converter U2 so that the output voltage VOUT of the operational amplifier U6 is 0. After adjustment, proceed with subsequent experiments.

[0028] In summary, this invention employs a reference voltage circuit to generate a high-precision, low-noise reference voltage. Then, a bipolar DC voltage circuit converts this reference voltage into a voltage within the positive and negative reference voltage range. This voltage also exhibits high precision and low noise. A voltage-to-current conversion circuit then converts this voltage into a compensation current. Finally, a transimpedance amplifier circuit cancels out the DC component and converts the AC component back into a voltage signal for output. This invention achieves high-precision current compensation with low noise characteristics.

[0029] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A transimpedance amplifier circuit with adjustable compensation current, characterized in that, It includes a reference voltage circuit, a bipolar DC voltage circuit, a voltage-to-current conversion circuit, and a transimpedance amplifier unit; The reference voltage circuit converts the power supply voltage into a reference voltage; the bipolar DC voltage circuit converts the reference voltage into positive and negative reference voltages; the voltage-to-current conversion circuit converts the positive and negative reference voltages into current. The transimpedance amplifier unit receives the current signal generated by the voltage-to-current conversion circuit, subtracts it from the current signal flowing into the input port, and then converts the subtracted current signal into a voltage signal for output. The bipolar DC voltage circuit includes a multiplier-type digital-to-analog converter U2, a capacitor C3, resistors R1, R2, and R3, an operational amplifier U3, and an operational amplifier U4. Specifically, the VREF terminal of the multiplier-type digital-to-analog converter U2 is connected to the output terminal VREF of the reference voltage chip U1 in the reference voltage circuit; the GND terminal is grounded; the VDD terminal is connected to the voltage source VDD; the IOUT terminal is connected to the negative input terminal of the operational amplifier U3; and the RFB terminal is connected to the output terminal of the operational amplifier U3. One end of the capacitor C3 is connected to the multiplier-type digital-to-analog converter... The RFB terminal of the multiplier-type digital-to-analog converter U2 is connected to the other end of the multiplier; the positive input terminal of the operational amplifier U3 is grounded, and the output terminal is connected to resistor R3; the other end of resistor R3 is connected to the negative input terminal of the operational amplifier U4; one end of resistor R1 is connected to the output terminal VREF of the reference voltage chip U1, and the other end of resistor R1 is connected to the negative input terminal of the operational amplifier U4; one end of resistor R2 is connected to the negative input terminal of the operational amplifier U4, and the other end is connected to the output terminal of the operational amplifier U4; the positive input terminal of the operational amplifier U4 is grounded. The voltage-to-current conversion circuit includes resistors R4, R5, R6, R8, and R9, and operational amplifier U5. One end of resistor R4 is connected to the negative input terminal of operational amplifier U5, and the other end is connected to the output terminal of operational amplifier U5. One end of resistor R5 is connected to the output terminal of operational amplifier U4, and the other end is connected to the negative input terminal of operational amplifier U5. One end of resistor R6 is connected to the output terminal of operational amplifier U5, and the other end is connected to the negative input terminal of operational amplifier U6 in the transimpedance amplification unit. One end of resistor R8 is connected to the bias voltage VBIAS, and the other end is connected to the positive input terminal of operational amplifier U5. One end of resistor R9 is connected to the positive input terminal of operational amplifier U5, and the other end is grounded. The current flowing through resistor R6 is ; in, VSHT is the output voltage of operational amplifier U5, and VBIAS is the bias voltage at the positive input terminal of operational amplifier U6. is the output voltage of operational amplifier U4, D is the control code of multiplier-type digital-to-analog converter U2, ISHT is the current flowing through resistor R6, n is the number of bits of multiplier-type digital-to-analog converter U2, and VREF is the reference voltage output by reference voltage chip U1.

2. The transimpedance amplifier circuit with adjustable compensation current as described in claim 1, characterized in that, The reference voltage circuit includes an input capacitor C1, a reference voltage chip U1, and an output capacitor C2. One end of capacitor C1 is grounded, and the other end is connected to the VIN terminal of the reference voltage chip U1. The GND terminal of the reference voltage chip U1 is grounded. One end of the output capacitor C2 is connected to the VREF terminal of the reference voltage chip U1, and the other end is grounded. The input capacitor C1 filters the power supply voltage. The reference voltage chip U1 converts the power supply voltage into a reference voltage signal. The output capacitor C2 filters the reference voltage signal.

3. The transimpedance amplifier circuit with adjustable compensation current as described in claim 1, characterized in that, The transimpedance amplifier unit includes a connector P1, a capacitor C4, a resistor R7, and an operational amplifier U6; wherein, the negative input terminal of the connector P1 is grounded; one end of the capacitor C4 is connected to the negative input terminal of the operational amplifier U6, and the other end is connected to the output terminal of the operational amplifier U6; one end of the resistor R7 is connected to the negative input terminal of the operational amplifier U6, and the other end is connected to the output terminal of the operational amplifier U6; the negative input terminal of the operational amplifier U6 is connected to the connector P1, and the positive input terminal is connected to the bias voltage VBIAS.

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