Isolating circuit for performance test of photoelectric detector

Abstract

The utility model relates to the technical field of photoelectric detector testing, and discloses an isolating circuit for photoelectric detector performance testing, which comprises a first loop and an operational amplifier circuit. Wherein the first loop comprises a bias power supply, a detector resistor and a matching resistor which are connected in series; the operational amplifier circuit comprises an input-stage operational amplifier circuit, an RC circuit and an output-stage operational amplifier circuit, one end of the input-stage operational amplifier circuit is connected between the detector resistor and the matching resistor, the other end of the input-stage operational amplifier circuit is connected with the output-stage operational amplifier circuit through the RC circuit, and the output-stage operational amplifier circuit is used for being connected with an electronic measuring instrument. According to the utility model, the operational amplifier is used for input stage impedance isolation, so that the defect that the RC circuit needs impedance matching with the detector resistor is overcome.

Description

Technical Field

[0001] The utility model relates to the technical field of photoelectric detector testing, in particular to an isolation circuit for photoelectric detector performance testing. Background Art

[0002] Infrared detectors are categorized as photovoltaic and photoconductive. Photovoltaic detectors have a built-in electric field, generating current when they absorb light. Photoconductive detectors are equivalent to photoresistors. Their resistance, Rd, changes with light absorption, but the detection signal requires an external bias. This requires a matching resistor, RL, connected in series with the circuit to establish a variable voltage test point between the two resistors, from which the detection signal is extracted.

[0003] Existing technologies offer testing solutions for photoconductive detectors, allowing for measurement of detector signals in the low resistance range. However, a drawback is that, for a fixed test frequency, the time constant of the RC circuit is typically also fixed. However, because the RC circuit is directly connected in parallel with the detector Rd, impedance matching between the RC circuit and the detector resistance is required. Otherwise, signal distortion will inevitably occur, affecting test accuracy.

[0004] For high-resistance detectors, the resistance value of the resistor Ra in the RC circuit that meets the impedance matching condition is too large, making selection difficult. In addition, detectors with different resistance values ​​need to be replaced frequently, affecting test efficiency. Utility Model Content

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an isolation circuit for photodetector performance testing, which uses an operational amplifier to perform input stage impedance isolation to optimize the shortcoming that the RC circuit needs to perform impedance matching with the detector resistance.

[0006] The utility model adopts the following technical solutions:

[0007] An isolation circuit for testing the performance of a photodetector includes a first loop and an operational amplifier circuit; wherein:

[0008] The first circuit includes a bias power supply, a detector resistor and a matching resistor connected in series;

[0009] The operational amplifier circuit includes an input-stage operational amplifier circuit, an RC circuit, and an output-stage operational amplifier circuit, wherein one end of the input-stage operational amplifier circuit is connected between the detector resistor and the matching resistor, and the other end of the input-stage operational amplifier circuit is connected to the output-stage operational amplifier circuit through the RC circuit, and the output-stage operational amplifier circuit is used to connect to an electronic measuring instrument.

[0010] Preferably, in the isolation circuit for the above-mentioned photodetector performance test, one end of the matching resistor is connected in series with one end of the detector resistor, the other end of the matching resistor is connected to the positive electrode of the bias power supply, and the other end of the detector resistor is connected to the negative electrode of the bias power supply.

[0011] Preferably, in the isolation circuit for the above-mentioned photodetector performance test, the RC circuit includes a resistor and a capacitor; the input end of the input-stage operational amplifier circuit is connected to a test point, which is a point between the detector resistor and the matching resistor; the output end of the input-stage operational amplifier circuit is connected to one end of the capacitor, and the other end of the capacitor is simultaneously connected to the resistor and the input end of the output-stage operational amplifier circuit; the output end of the output-stage operational amplifier circuit is connected to an electronic measuring instrument, and the end of the resistor not connected to the capacitor is grounded.

[0012] Preferably, in the above-mentioned isolation circuit for testing the performance of the photodetector, the resistance of the matching resistor matches the resistance of the detector resistor in the absence of light.

[0013] Preferably, in the isolation circuit for the above-mentioned photodetector performance test, the input and output signals of the input-stage operational amplifier circuit are equal, and the gain is 1.

[0014] Preferably, in the isolation circuit for the above-mentioned photodetector performance test, the input-stage operational amplifier circuit includes an operational amplifier and a feedback resistor and a grounding resistor connected to the operational amplifier; wherein the feedback resistor and the grounding resistor are used to jointly determine the gain of the input-stage operational amplifier circuit.

[0015] Preferably, in the above-mentioned isolation circuit for photodetector performance testing, the input-stage operational amplifier circuit is a follower or a non-inverting amplifier.

[0016] Preferably, in the above-mentioned isolation circuit for photodetector performance testing, the electronic measuring instrument is an oscilloscope.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] The isolation circuit for testing photodetector performance proposed in this utility model adds an input-stage op amp circuit and an output-stage op amp circuit to the existing RC circuit to form an op amp circuit. The input-stage op amp circuit isolates the detector impedance from the RC circuit impedance. The high input impedance and low output impedance provided by the op amp simultaneously meet the impedance matching requirements of the detector resistance and the RC circuit. The output-stage op amp circuit also improves the load capacity. With this improved isolation circuit, even detector resistances as high as hundreds of megohms will not affect the sampling accuracy of the RC circuit, thus enabling performance testing of detectors with both low and high resistance values, greatly improving testing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0020] Figure 1 A schematic diagram of an isolation circuit for testing the performance of a photodetector;

[0021] Figure 2 This is a schematic diagram of an isolation circuit for testing the performance of a photodetector when a follower is used as an input stage operational amplifier circuit;

[0022] Figure 3 This is a schematic diagram of an isolation circuit for testing the performance of a photodetector using a non-inverting amplifier as an input stage operational amplifier circuit;

[0023] Figure 4 This is the circuit structure and signal output diagram when the resistance of the detector without input stage op amp is 0.01M;

[0024] Figure 5 This is the circuit structure and signal output diagram when the resistance of the detector without input stage op amp is 1M;

[0025] Figure 6 This is the circuit structure and signal output diagram when there is no input stage op amp and the detector resistance is 100M;

[0026] Figure 7 This is the circuit structure and signal output diagram when the input stage operational amplifier detector resistance is 0.01M;

[0027] Figure 8 This is the circuit structure and signal output diagram when the input stage operational amplifier detector resistance is 1M;

[0028] Figure 9 This is the circuit structure and signal output diagram when there is an input-stage operational amplifier and the detector resistance is 100M. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different perspectives and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features within these embodiments may be combined with one another, unless they conflict.

[0030] In the description of this utility model, unless otherwise specified, "plurality" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this utility model and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific direction, be constructed, or operate in a specific direction, and therefore should not be construed as limiting this utility model. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] In the description of this utility model, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on specific circumstances.

[0032] The present invention will now be further described with reference to the accompanying drawings.

[0033] Please combine Figures 4 to 6 As shown, Figures 4 to 6 The left side of the figure shows the isolation circuit diagram of the detector performance test without input operational amplifier in the prior art. In the prior art, there is only an RC circuit, and the RC circuit and the detector resistance need to meet the impedance matching, otherwise it will inevitably cause signal distortion and affect the test accuracy.

[0034] Based on this, the embodiment of the present invention provides an isolation circuit for testing the performance of a photodetector, such as Figure 1 As shown, the isolation circuit for the photodetector performance test includes a first loop 100 and an operational amplifier circuit 200; wherein the first loop 100 includes a bias power supply V, a detector resistor R connected in series d And matching resistor R LThe operational amplifier circuit 200 includes an input stage operational amplifier circuit AMP1, an RC circuit, and an output stage operational amplifier circuit AMP2, wherein one end of the input stage operational amplifier circuit AMP1 is connected to the detector resistor R d and matching resistor R L The other end of the input-stage operational amplifier circuit AMP1 is connected to the output-stage operational amplifier circuit AMP2 through an RC circuit. The output-stage operational amplifier circuit AMP2 is used to connect to an electronic measuring instrument.

[0035] In this embodiment, by designing the operational amplifier circuit 200, an input stage operational amplifier circuit AMP1 and an output stage operational amplifier circuit AMP2 are added to the original operational amplifier circuit which only has an RC circuit. During the test, the detector resistance R d Exposure to light of a certain frequency hv causes a change in resistance. This, combined with the applied bias voltage from the bias power supply V, generates a pulsating DC voltage signal, which is then output to the RC circuit to filter out the DC component. Input-stage op amp Amp1 then provides impedance isolation, while output-stage op amp Amp2 increases load capacity. This isolation circuit uses op amps for input-stage impedance isolation, eliminating the RC circuit's need for impedance matching with the detector's resistor.

[0036] It should be noted that the detector resistance R d It is a photosensitive element in a photodetector. When the photosensitive element is exposed to light, its resistance value will change, thus causing the electrical signal to change. By measuring the detector resistance R d The change of the electrical signal in the first loop 100 can reflect the change of the optical signal.

[0037] In some embodiments, as Figure 1 As shown, the specific structure of the first loop 100 can be: matching resistor R L One end of the detector resistor R d One end is connected in series with the matching resistor R L The other end is connected to the positive electrode of the bias power supply V, and the detector resistor R d The other end is connected to the negative terminal of the bias power supply V.

[0038] In some embodiments, as Figure 1 As shown, the RC circuit includes a resistor R a and capacitor C; the input end of the input stage operational amplifier circuit AMP1 is connected to test point A, which is the detector resistance R d and matching resistor R L The output end of the input stage operational amplifier circuit AMP1 is connected to one end of the capacitor C, and the other end of the capacitor C is connected to the resistor R aAnd the input end of the output stage operational amplifier circuit AMP2, the output end of the output stage operational amplifier circuit AMP2 is connected to the electronic measuring instrument, the resistor R a The end not connected to capacitor C is grounded.

[0039] In some embodiments, the matching resistor R L The resistance value of the detector is R d The resistance values ​​in the absence of light match.

[0040] For example, the matching resistor R L The resistance value of the detector is R d The way to match the resistance value in the absence of light can be to match the resistor R L The resistance value of the detector is R d Under no light, the resistance is equal. It is understandable that the above resistance matching method is only an example and is not a limitation of the present invention. In other embodiments, the matching resistor R L The resistance value of the detector is R d Another method of matching the resistance values ​​when there is no light is to match the two at other set ratio values.

[0041] In some embodiments, the input-stage operational amplifier circuit AMP1 is a follower or a non-inverting amplifier.

[0042] like Figure 2 As shown, the input stage operational amplifier circuit AMP1 is a follower. Figure 2 In the circuit structure shown, the matching resistor R L The resistance value of the detector is R d The resistance value in the absence of light matches the detector resistance R d Exposure to light of a certain frequency causes a change in resistance. Under the action of an external bias voltage, a pulsating DC voltage signal is generated at test point A. This signal is then filtered out by an RC circuit to remove the DC component and then output to the electronic measuring instrument via output-stage op amp AMP2. At this point, input-stage op amp AMP1 functions as a follower with a gain of 1. The signals at the op amp's input and output are equal, and input-stage op amp AMP1 serves only as impedance isolation.

[0043] like Figure 3 As shown, the input stage operational amplifier circuit AMP1 is a non-inverting amplifier. Figure 3 In the circuit structure shown, the matching resistor R L The resistance value of the detector is R d The resistance value in the absence of light matches the detector resistance R dAfter being irradiated by light of a certain frequency, the resistance value changes. Under the action of the external bias, a pulsating DC voltage signal is generated at the test point A, which is output to the RC circuit to filter out the DC part and output to the electronic measuring instrument through the output stage operational amplifier circuit AMP2. At this time, the output stage operational amplifier circuit Amp1 is a non-inverting amplifier, and the gain is determined by the feedback resistor R f and grounding resistance R g The output signal is amplified by a certain multiple, and the output stage operational amplifier circuit Amp1 is used as both impedance isolation and amplifier.

[0044] In some embodiments, the electronic measuring instrument is an existing instrument capable of measuring electrical signals, such as an oscilloscope. Of course, the electronic measuring instrument can also be other instruments capable of measuring electrical signals, such as a voltmeter, an ammeter, a multimeter, etc. This embodiment is merely an example and does not limit the present invention.

[0045] The effectiveness of the present invention will be further illustrated below with reference to specific test cases.

[0046] like Figures 4 to 6 As shown, it shows the test results of the isolation circuit of the detector performance test without input stage operational amplifier in the prior art. Figures 7 to 9 As shown in FIG, it shows the test results of the isolation circuit of the photodetector performance test proposed in this embodiment. This embodiment provides six test cases. Figures 4 to 9 In the figure, V1 represents the selected bias power supply, R1 and R2 represent the specific resistance of the detector resistor in the dark and the specific resistance of the matching resistor, respectively. In each test case, R1 and R2 are equal. C1 and R3 represent the capacitor and resistor in the RC circuit. In all six test cases, C1 and R3 are equal, with C1 = 1 μf and R3 = 10 MΩ. XSC1 represents the oscilloscope. The same model of oscilloscope was used in all test cases. Figures 7 to 9 In the figure, the input stage op amp circuit used is a follower, and the output stage op amp circuit is not shown, which can be configured in the connector connected to the oscilloscope.

[0047] The detailed descriptions of the six test cases are as follows:

[0048] Test Example 1: Testing of the isolation circuit for the detector performance test without an input op amp, where R1 = R2 = 0.01MΩ; C1 = 1μf, R3 = 10MΩ. Radiation of a set frequency f is used to irradiate the detector resistor, and the waveform of the electrical signal is obtained through an oscilloscope. The results are as follows: Figure 4 shown.

[0049] Test Example 2: Testing of the isolation circuit for the performance test of a detector without an input stage op amp, where R1 = R2 = 1MΩ; C1 = 1μf, R3 = 10MΩ. Radiation of a set frequency f is used to irradiate the detector resistor, and the waveform of the electrical signal is obtained through an oscilloscope. The results are as follows: Figure 5 shown.

[0050] Test Example 3: Testing the isolation circuit of a detector without an input op amp, where R1 = R2 = 100MΩ; C1 = 1μf, R3 = 10MΩ. Radiation of a set frequency f is used to irradiate the detector resistor, and the waveform of the electrical signal is obtained through an oscilloscope. The results are as follows: Figure 6 shown.

[0051] Test Example 4: Test of the isolation circuit for photodetector performance test, where R1 = R2 = 0.01MΩ; C1 = 1μf, R3 = 10MΩ, use radiation of set frequency f to irradiate the detector resistor, and obtain the waveform of the electrical signal through the oscilloscope. The results are as follows Figure 7 shown.

[0052] Test Example 5: Test of the isolation circuit for photodetector performance test, where R1 = R2 = 1MΩ; C1 = 1μf, R3 = 10MΩ, use radiation of set frequency f to irradiate the detector resistor, and obtain the waveform of the electrical signal through the oscilloscope. The results are as follows Figure 8 shown.

[0053] Test Example 6: Photoelectric detector performance test of the isolation circuit, where R1 = R2 = 100MΩ; C1 = 1μf, R3 = 10MΩ, use the radiation of the set frequency f to irradiate the detector resistor, and use the oscilloscope to obtain the waveform of the electrical signal. The results are as follows Figure 9 shown.

[0054] like Figure 4 、 Figure 5 and Figure 6 As shown in the figure, for different detector resistances, if the selection of the RC circuit is not adjusted (the values ​​of C1 and R3 in different types of RC circuits are not equal), the overall fluctuation of the detected waveform is large. Figure 7 、 Figure 8 and Figure 9 As shown in FIG, for different detector resistances, even without adjusting the RC circuit, the detected waveforms remain substantially consistent. Therefore, compared to conventional test circuits, the circuit proposed in this embodiment has the following advantages:

[0055] 1. For high-resistance detector testing, there is no need to use the ultra-high resistance R3 for impedance matching.

[0056] 2. For the testing needs of detectors with different resistance values, there is no need to frequently replace the RC circuit.

[0057] 3. The circuit structure is more reliable and the test results are more accurate.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. An isolation circuit for photodetector performance testing, characterized in that: It includes a first loop and an operational amplifier circuit; wherein: The first circuit includes a bias power supply, a detector resistor and a matching resistor connected in series; The operational amplifier circuit includes an input-stage operational amplifier circuit, an RC circuit, and an output-stage operational amplifier circuit, wherein one end of the input-stage operational amplifier circuit is connected between the detector resistor and the matching resistor, and the other end of the input-stage operational amplifier circuit is connected to the output-stage operational amplifier circuit through the RC circuit, and the output-stage operational amplifier circuit is used to connect to an electronic measuring instrument.

2. The isolation circuit for photodetector performance testing according to claim 1, characterized in that: One end of the matching resistor is connected in series with one end of the detector resistor, the other end of the matching resistor is connected to the positive electrode of the bias power supply, and the other end of the detector resistor is connected to the negative electrode of the bias power supply.

3. The isolation circuit for photodetector performance testing according to claim 1, characterized in that: The RC circuit includes a resistor and a capacitor; the input end of the input-stage operational amplifier circuit is connected to a test point, which is a point between the detector resistor and the matching resistor; the output end of the input-stage operational amplifier circuit is connected to one end of the capacitor; the other end of the capacitor is simultaneously connected to the resistor and the input end of the output-stage operational amplifier circuit; the output end of the output-stage operational amplifier circuit is connected to an electronic measuring instrument; and the end of the resistor not connected to the capacitor is grounded.

4. The isolation circuit for photodetector performance testing according to claim 1, characterized in that: The resistance of the matching resistor matches the resistance of the detector resistor when there is no light.

5. The isolation circuit for photodetector performance testing according to claim 1, characterized in that: The input and output signals of the input stage operational amplifier circuit are equal, and the gain is 1.

6. The isolation circuit for photodetector performance testing according to claim 1, characterized in that: The input stage operational amplifier circuit includes an operational amplifier and a feedback resistor and a grounding resistor connected to the operational amplifier; wherein the feedback resistor and the grounding resistor are used to jointly determine the gain of the input stage operational amplifier circuit.

7. The isolation circuit for photodetector performance testing according to claim 1, characterized in that: The input stage operational amplifier circuit is a follower or a non-inverting amplifier.

8. The isolation circuit for photodetector performance testing according to claim 1, characterized in that: The electronic measuring instrument is an oscilloscope.

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