A high-gain i-v conversion circuit transimpedance gain in-situ calibration method and system

Abstract

The application relates to the technical field of weak electric signal detection and precision calibration, and discloses a high-gain current-voltage converter transimpedance gain in-situ calibration method and system. The method sets an in-situ calibration structure of an isolable operational amplifier feedback network, constructs a high-impedance measuring device based on a double-power Wheatstone bridge, adopts a linear fitting and current detection residual correction method, and realizes accurate calibration of a G omega level feedback network impedance; taking the calibrated transfer standard current-voltage converter as a core, a value transmission link of "high resistance standard-transfer standard current-voltage converter-precision current source-to-be-measured transimpedance amplifier" is established, pA level micro-current source calibration and absolute calibration of high-gain transimpedance amplifier transimpedance gain are realized, and an error transmission and uncertainty model is established to quantitatively control the calibration process. The application can calibrate the pA level output of a commercial precision current source with high precision without large precision auxiliary equipment such as a low-temperature current comparator, realizes high-precision micro-current value transmission and transimpedance gain calibration under low-cost conditions, overcomes the defects of high auxiliary equipment cost, complex process and low precision of the current-voltage converter gain calibration method in the prior art, and is suitable for micro-light detection and precision measurement fields.

Description

Technical Field

[0001] This invention relates to the field of weak electrical signal detection and precision calibration technology, and in particular to a method and system for in-situ calibration of transimpedance gain of a high-gain IV converter circuit. Background Technology

[0002] In the field of pA-level weak photocurrent detection, the transimpedance amplifier (TIA), as the core current-to-voltage converter, directly determines the accuracy of weak current measurement through the calibration accuracy of its transimpedance gain. This is a key technical aspect of high-precision photodetector systems and other equipment. Existing gain calibration methods for high-gain IV (current-to-voltage) converters mainly include the capacitor charging method, the low-temperature current comparator (CCC) calibration source method, the traceability method for transmitted standard current-to-voltage converters, the ultra-stable low-noise current amplifier (ULCA) calibration method, and the external resistor method. However, these methods have many technical drawbacks. Relying on external, sophisticated and large auxiliary equipment (such as low-temperature current comparators (CCC), multiple high-precision digital multimeters, standard resistance standard systems, etc.), the equipment is expensive and bulky, and cannot meet the on-site calibration needs of basic laboratories and engineering scenarios. The calibration process is cumbersome and complex, and most of it is done offline. Disassembly, wire connection and other processes can easily introduce parasitic errors, which can lead to a decrease in calibration accuracy. Commercial precision current sources have limited accuracy when outputting in the pA range (e.g., accuracy is only 1% ± 10fA when outputting 1pA), and cannot be directly used as standard current sources for high-gain TIA calibration. Summary of the Invention

[0003] To overcome the shortcomings of existing current-to-voltage converter gain calibration methods, such as high cost of auxiliary equipment, complex process, and low accuracy, this invention proposes an in-situ calibration method for the transimpedance gain of a high-gain current-to-voltage converter. This method eliminates the need for large and precise external auxiliary equipment, achieves in-situ closed-loop impedance calibration of the feedback network, and removes parasitic errors introduced by disassembly, wiring, and operational amplifier active parameters, thereby improving calibration accuracy.

[0004] This invention proposes an in-situ calibration method for the transimpedance gain of a high-gain current-to-voltage converter, comprising the following steps: S1. Set up the test circuit, including: a test voltage source, a calibration voltage source, an ammeter, a standard reference resistor, and the current-to-voltage converter to be tested; the test voltage source and the current-to-voltage converter are connected in series to form the first branch, and the calibration voltage source and the standard reference resistor are connected in series to form the second branch; the first branch and the second branch form two parallel branches of the ammeter; the ammeter reading is the current difference between the first branch and the second branch. S2. Fix the output voltage of the calibration voltage source and denote it as the calibration voltage Vs; S3. Adjust the output voltage of the voltage source to E1 and read the ammeter reading ΔI1; adjust the output voltage of the voltage source to E2 and read the ammeter reading ΔI2. S4. Calculate the theoretical equilibrium voltage. Set the output voltage of the voltage source to be adjusted. And read the ammeter reading ΔI;

[0005] S5. Calculate the feedback resistor Rx of the current-to-voltage converter:

[0006]

[0007] Where Rs is the resistance value of the standard reference resistor; Is is the current in the second branch.

[0008] Preferably, the ratio of E1 to the calibration voltage Vs is greater than 10 or less than 0.1, and the ratio of E2 to the calibration voltage Vs is greater than 10 or less than 0.1.

[0009] Preferably, the ratio of E1 to calibration voltage Vs is greater than 10, and the ratio of E2 to calibration voltage Vs is less than 0.1.

[0010] Preferably, the current-to-voltage converter is housed entirely within an electromagnetic shielding device.

[0011] Preferably, the formula for calculating the uncertainty u(Rx) of the feedback resistor Rx is:

[0012] Where c1, c2, c3 and c4 represent the sensitivity coefficients of the test voltage source Ux, the calibration voltage source Us, the standard reference resistor and the ammeter, respectively; u(Ux), u(Us), u(Rs) and u(ΔI / I) represent the uncertainties of the test voltage source Ux, the calibration voltage source Us, the standard reference resistor and the ammeter, respectively.

[0013] Preferred:

[0014]

[0015]

[0016]

[0017] in, This indicates differentiation.

[0018] This invention proposes a high-gain IV converter transimpedance gain in-situ calibration system for implementing the aforementioned high-gain current-to-voltage converter transimpedance gain in-situ calibration method. The system includes a test platform comprising: a test voltage source Ux, a calibration voltage source Us, an ammeter, a standard reference resistor, and a test station for connecting the current-to-voltage converter (TS CVC) under test. When the current-to-voltage converter is connected to the test station, the test voltage source Ux and the current-to-voltage converter are connected in series to form a first branch, and the calibration voltage source Us and the standard reference resistor are connected in series to form a second branch. The first and second branches form two parallel branches of the ammeter.

[0019] Preferably, it also includes a computer, which is used to control the output voltage of the debugging voltage source Ux and to read the ammeter reading; during the test, the computer executes the high-gain current-voltage converter transimpedance gain in-situ calibration method as described in any one of claims 1-6, and calculates the feedback resistance Rx of the current-voltage converter.

[0020] The present invention proposes a current source calibration method, which first calibrates the feedback resistor of the current-voltage converter using the aforementioned high-gain current-voltage converter transimpedance gain in-situ calibration method. Then, the current source to be calibrated is connected to the current input terminal of the current-to-voltage converter, and the first voltmeter is connected to the voltage output terminal of the current-to-voltage converter. When the current source output current is 0, the voltage value measured by the first voltmeter is recorded as the offset voltage V1 (I=0); when the current source has an output, the voltage value measured by the first voltmeter is recorded as the output voltage V1 (I). When the output voltage is V1(I), the calibration value I of the current source output current is: .

[0021] This invention proposes a method for calibrating the transimpedance gain of a photodetector preamplifier circuit, comprising the following steps: St1. Connect the current source to the photodetector under test and inject current into the preamplifier circuit of the photodetector under test through the current source; connect the second voltmeter to the output terminal of the preamplifier circuit of the photodetector under test; when the current source has no output, the voltage value measured by the second voltmeter is recorded as the offset voltage V2 (I=0); St2, start the current source to output current, and record the voltage value measured by the second voltmeter as the output voltage V2(I); use the current source calibration method as described in claim 7 to obtain the calibration value I of the current source output current; St3, calculate the actual transimpedance gain G(I) of the preamplifier circuit of the photodetector under test when the calibration value of the current source is I: .

[0022] The advantages of this invention are: (1) This invention proposes an in-situ calibration method for the transimpedance gain of a high-gain IV converter circuit, used to calculate the resistance value of the feedback resistor of the current-to-voltage converter. This invention obtains a linear relationship between the output voltage of the ammeter reading and the output voltage of the ammeter reading by applying the output voltage of the debugging voltage source Ux twice, thereby accurately solving for the voltage required for bridge balancing. This replaces manual adjustment, improving calibration efficiency and accuracy. Applying... Afterwards, the bridge approaches equilibrium, and combined with the corrected formula for calculating the measured impedance, it compensates for the measurement error of the traditional Wheatstone bridge.

[0023] (2) The test circuit of the present invention is an improved dual-power Wheatstone bridge, which achieves bridge balance through linear fitting. The improved dual-power Wheatstone bridge effectively suppresses leakage current and electromagnetic interference in GΩ-level high resistance measurement, solves the technical bottleneck that the traditional Wheatstone bridge is only suitable for medium and low resistance measurement, and realizes accurate measurement of high-gain feedback network.

[0024] (3) The present invention proposes a high-gain IV conversion circuit transimpedance gain in-situ calibration system. By connecting the current-voltage converter at the test station, the in-situ closed-loop impedance calibration of the feedback resistor is achieved. The circuit does not need to be disassembled, and the parasitic errors introduced by the leads, assembly and operational amplifier active parameters are eliminated. Compared with the traditional offline calibration method, the calibration accuracy is significantly improved. (4) This invention is applicable to in-situ calibration of the transimpedance gain of high-gain transimpedance amplifiers (TIAs) with pA-level microcurrent detection, and can be applied to the gain calibration of high-impedance current-to-voltage converters in fields such as space radiation reference, photoelectric detection, and precision metrology. Using this invention, a hardware system adapted to in-situ calibration can be designed, realizing the standardization and simplification of the calibration process, and improving the convenience and practicality of engineering applications.

[0025] (5) This invention constructs a complete error propagation and uncertainty model by calculating the uncertainty of the feedback resistor of the current-to-voltage converter, which can strictly control various errors in the calibration process and make the calibration uncertainty of the high-gain IV conversion circuit meet the system index requirements of pA-level microcurrent detection. (6) The current source calibration method proposed in this invention uses a calibrated current-to-voltage converter for current source calibration, which solves the problem of insufficient output accuracy of commercial precision current sources in the pA range. It can ensure current output accuracy while controlling the cost of the current source. The corrected current source can be used as a standard source for high-gain TIA calibration without the need for additional customization of high-end precision current sources, thus reducing equipment costs. During the testing process, the hardware structure is simplified, the operation is convenient, and the engineering practicality is strong: the calibration system does not require large external precision auxiliary equipment, the TS-CVC (current-to-voltage converter) hardware structure is compact, the calibration process is standardized, and it can be adapted to the on-site calibration needs of basic laboratories and engineering scenarios, thereby enhancing the application value of the technology.

[0026] (7) This invention proposes a method for calibrating the transimpedance gain of a photodetector preamplifier circuit. The method uses a calibrated current source for testing, which is low in cost, simple to operate, and has reliable test results. Attached Figure Description

[0027] Figure 1 This is a flowchart of an in-situ calibration method for the transimpedance gain of a high-gain IV-conversion circuit. Figure 2 Schematic diagram of TS-CVC gain in-situ calibration; Figure 3 Schematic diagram for current source calibration; Figure 4 This is the calibration schematic for the high-gain preamplifier circuit under test. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, the present invention proposes an in-situ calibration method for the transimpedance gain of a high-gain IV-conversion circuit, comprising the following steps: S1, Setup Figure 2 The test circuit shown includes: a debugging voltage source Ux, a calibration voltage source Us, an ammeter, and a standard reference resistor R. ref And the current-to-voltage converter under test (TS CVC); debug the voltage source Ux and the current-to-voltage converter in series to form the first branch, and calibrate the voltage source Us and the standard reference resistor R. ref The first and second branches are connected in series to form the second branch; the first and second branches form two parallel branches of the ammeter.

[0030] The ammeter reading is the difference between the currents in the first branch and the second branch. When the currents in the first branch and the second branch are balanced, theoretically, the ammeter should measure a current of 0.

[0031] S2. The output voltage of the fixed calibration voltage source Us is denoted as the calibration voltage Vs; S3. Adjust the output voltage of the voltage source Ux to E1 and read the ammeter reading ΔI1; adjust the output voltage of the voltage source Ux to E2 and read the ammeter reading ΔI2.

[0032] In practice, the greater the difference between the output voltage of the debugging voltage source Ux and the calibration voltage Vs, the greater the ammeter reading. For ease of calculation, the ratio of E1 to the calibration voltage Vs can be set to be greater than 10 or less than 0.1, and the ratio of E2 to the calibration voltage Vs can be greater than 10 or less than 0.1. To further facilitate subsequent calculations, the ratio of E1 to the calibration voltage Vs can be further set to be greater than 10, and the ratio of E2 to the calibration voltage Vs can be less than 0.1.

[0033] S4. Calculate the theoretical equilibrium voltage. Set the output voltage of the voltage source Ux to be adjusted to And read the ammeter reading ΔI;

[0034] S5. Calculate the feedback resistor Rx of the current-to-voltage converter:

[0035] (3) Where Rs is the standard reference resistance R ref The resistance value.

[0036] In practical implementation, the feedback resistor and the standard reference resistor R of the current-to-voltage converter... ref All are placed in an electromagnetic shielding device, thereby effectively suppressing leakage current and spatial interference in high-resistance measurements.

[0037] This invention proposes an in-situ calibration system for the transimpedance gain of a high-gain IV-to-IV converter circuit, comprising a test platform and a computer; the test platform includes: a debugging voltage source Ux, a calibration voltage source Us, an ammeter, and a standard reference resistor R. ref And a test station for connecting the current-to-voltage converter under test (TS CVC); When the current-to-voltage converter is connected to the test station, the voltage source Ux and the current-to-voltage converter are connected in series to form the first branch, and the voltage source Us and the standard reference resistor R are calibrated. ref The first and second branches are connected in series to form the second branch; the first and second branches form two parallel branches of the ammeter.

[0038] The computer is used to control the output voltage of the debugging voltage source Ux and to read the ammeter readings.

[0039] In practice, the computer can control the output voltage of the debugging voltage source Ux twice and read the ammeter reading, and then substitute it into formula (1)-formula (3) to calculate the feedback resistance Rx of the current-voltage converter.

[0040] according to Figure 2 The experimental setup shown evaluates the uncertainty components of the overall test results, including the following four parts: 1) Adjust the output uncertainty component u(Ux) of the voltage source Ux; 2) Calculate the output uncertainty component u(Us) of the calibration voltage source Us; 3) The relative standard uncertainty u(Rs) of the standard reference resistor; 4) The uncertainty of the ammeter, u(ΔI / I); According to the Guide to Measurement Uncertainty Assessment (GUM), the output quantity Rx is a nonlinear function of the input quantities Us, Ux, Rs, and ΔI / I. Since the input quantities are independent during the measurement process, their covariance is zero. Based on the error propagation law, the combined standard uncertainty u(Rx) of Rx can be expressed as:

[0041] Where c1, c2, c3, and c4 represent the sensitivity coefficients of the debugging voltage source Ux, the calibration voltage source Us, the standard reference resistor, and the ammeter, respectively, and the calculation formula is:

[0042]

[0043]

[0044]

[0045] in, This indicates differentiation.

[0046] As can be seen from the uncertainty u(Rx), the limiting accuracy of the TS-CVC calibration link is determined by four core elements. To achieve low-uncertainty calibration, not only are extremely low standard uncertainties u(Ux) and u(Us) required for the dual-channel voltage sources (adjustment voltage source Ux and calibration voltage source Us), but also extremely high long-term stability and extremely low temperature coefficient of the standard reference resistor are required to reduce u(Rs). At the same time, the picoammeter (i.e., ammeter) needs to have extremely high current resolution to suppress the negative impact of current sensing residual fluctuation u(ΔI / I) on the overall resistance calculation.

[0047] After calibrating the current-to-voltage converter, it can be used to calibrate the current source, solving the problem of low output current accuracy of commercial current sources.

[0048] When calibrating the current source, first use the calibrated current-to-voltage converter to build, as shown in the example. Figure 3 The calibration current shown is as follows: connect the current source to be calibrated to the current input terminal of the current-to-voltage converter, and connect the first voltmeter to the voltage output terminal of the current-to-voltage converter.

[0049] When the current source outputs a certain current value I1, the output current can be calibrated using the following formula to obtain the actual output current of the current source, i.e., the calibration value I of the current value I1:

[0050] in, V1 represents the voltage value measured by the first voltmeter when the current source outputs a current value of I1; V1 (I=0) represents the voltage value measured by the first voltmeter when the current source has no current output. This represents the feedback resistor of the current-to-voltage converter.

[0051] This embodiment also proposes a method for calibrating the transimpedance gain of the photodetector's preamplifier circuit. A calibrated current source is used to inject current into the preamplifier circuit of the photodetector under test. During the test, a second voltmeter is connected to the output terminal of the preamplifier circuit of the photodetector under test to measure the output voltage. Figure 4 As shown.

[0052] During the test, firstly, when the current source outputs a certain current value I1, the above formula is used for calibration to obtain the calibration value I of the current value I1; then, the output voltage V2(I) of the preamplifier circuit when the current source outputs a current value I1 is measured by the second voltmeter; and the transimpedance gain G(I) of the preamplifier circuit when the current source outputs a current value I1 is calculated using the following formula:

[0053] Where V2 (I=0) represents the voltage value measured by the second voltmeter when the current source has no current output; This represents the calibration value of the current value I1.

[0054] In practice, a series of current values ​​output by the current source can be tested to obtain the actual output current and transimpedance gain G(I) corresponding to different calibration values ​​I.

[0055] In practice, assuming the maximum nominal output current of the current source is 5nA, the actual output current range of 0~4nA can be tested in a certain step, such as 30pA; thus, taking 80% of the nominal range ensures the test margin and the effectiveness of the test.

[0056] In this embodiment, the first voltmeter and the second voltmeter measure different objects. Specifically, the same voltmeter can be used. It is first used as the first voltmeter to calibrate the current source, and then used as the second voltmeter to test the transimpedance gain G(I) of the preamplifier circuit. Specifically, in this embodiment, the preamplifier circuit to be tested is a high-gain transimpedance amplifier circuit.

[0057] Of course, those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0058] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0059] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A method for in-situ calibration of transimpedance gain in a high-gain IV-to-IV converter circuit, characterized in that, Includes the following steps: S1. Set up the test circuit, including: a test voltage source, a calibration voltage source, an ammeter, a standard reference resistor, and the current-to-voltage converter to be tested; the test voltage source and the current-to-voltage converter are connected in series to form the first branch, and the calibration voltage source and the standard reference resistor are connected in series to form the second branch; the first branch and the second branch form two parallel branches of the ammeter; the ammeter reading is the current difference between the first branch and the second branch. S2. Fix the output voltage of the calibration voltage source and denote it as the calibration voltage Vs; S3. Adjust the output voltage of the voltage source to E1 and read the ammeter reading ΔI1; adjust the output voltage of the voltage source to E2 and read the ammeter reading ΔI2. S4. Calculate the theoretical equilibrium voltage. Set the output voltage of the voltage source to be adjusted. And read the ammeter reading ΔI; S5. Calculate the feedback resistor Rx of the current-to-voltage converter: Where Rs is the resistance value of the standard reference resistor; Is is the current in the second branch.

2. The in-situ calibration method for transimpedance gain of a high-gain IV-to-IV converter circuit as described in claim 1, characterized in that, The ratio of E1 to the calibration voltage Vs is greater than 10 or less than 0.1, and the ratio of E2 to the calibration voltage Vs is greater than 10 or less than 0.

1.

3. The in-situ calibration method for transimpedance gain of a high-gain IV-to-IV converter circuit as described in claim 2, characterized in that, The ratio of E1 to calibration voltage Vs is greater than 10, and the ratio of E2 to calibration voltage Vs is less than 0.

1.

4. The in-situ calibration method for transimpedance gain of a high-gain IV-conversion circuit as described in claim 1, characterized in that, The current-to-voltage converter is housed within an electromagnetic shielding device.

5. The in-situ calibration method for transimpedance gain of a high-gain IV converter circuit as described in claim 1, characterized in that, The formula for calculating the uncertainty u(Rx) of the feedback resistor Rx is: Where c1, c2, c3 and c4 represent the sensitivity coefficients of the test voltage source Ux, the calibration voltage source Us, the standard reference resistor and the ammeter, respectively; u(Ux), u(Us), u(Rs) and u(ΔI / I) represent the uncertainties of the test voltage source Ux, the calibration voltage source Us, the standard reference resistor and the ammeter, respectively.

6. The in-situ calibration method for transimpedance gain of a high-gain IV-conversion circuit as described in claim 5, characterized in that: in, This indicates differentiation.

7. A high-gain IV converter transimpedance gain in-situ calibration system, used to implement the high-gain current-to-voltage converter transimpedance gain in-situ calibration method as described in claim 1; characterized in that, The test platform includes: a test voltage source Ux, a calibration voltage source Us, an ammeter, a standard reference resistor, and a test station for connecting the current-to-voltage converter under test (TSCVC). When the current-to-voltage converter is connected to the test station, the test voltage source Ux and the current-to-voltage converter are connected in series to form the first branch, and the calibration voltage source Us and the standard reference resistor are connected in series to form the second branch. The first branch and the second branch form two parallel branches of the ammeter.

8. The high-gain IV-to-IV converter transimpedance gain in-situ calibration system as described in claim 7, characterized in that, It also includes a computer, which is used to control the output voltage of the debugging voltage source Ux and to read the ammeter reading; during the test, the computer executes the in-situ calibration method for the transimpedance gain of the high-gain current-voltage converter as described in any one of claims 1-6, and calculates the feedback resistance Rx of the current-voltage converter.

9. A current source calibration method employing the in-situ calibration method for the transimpedance gain of a high-gain IV converter circuit as described in any one of claims 1-6, characterized in that, First, the feedback resistor of the current-to-voltage converter is calibrated using the in-situ calibration method for the transimpedance gain of the high-gain IV conversion circuit as described in any one of claims 1-6. Then, the current source to be calibrated is connected to the current input terminal of the current-to-voltage converter, and the first voltmeter is connected to the voltage output terminal of the current-to-voltage converter. When the current source output current is 0, the voltage value measured by the first voltmeter is recorded as the offset voltage V1 (I=0); when the current source has an output, the voltage value measured by the first voltmeter is recorded as the output voltage V1 (I). When the output voltage is V1(I), the calibration value I of the current source output current is: 。 10. A method for calibrating the transimpedance gain of a photodetector preamplifier circuit using the current source calibration method as described in claim 9, characterized in that, Includes the following steps: St1. Connect the current source to the photodetector under test and inject current into the preamplifier circuit of the photodetector under test through the current source; connect the second voltmeter to the output terminal of the preamplifier circuit of the photodetector under test; when the current source has no output, the voltage value measured by the second voltmeter is recorded as the offset voltage V2 (I=0); St2, start the current source to output current, and record the voltage value measured by the second voltmeter as the output voltage V2(I); use the current source calibration method as described in claim 7 to obtain the calibration value I of the current source output current; St3, calculate the actual transimpedance gain G(I) of the preamplifier circuit of the photodetector under test when the calibration value of the current source is I: 。

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