Current testing device of silicon photomultiplier

Abstract

The utility model discloses a current testing device of a silicon photomultiplier, and belongs to the technical field of photoelectric testing technologies. The current testing device of the silicon photomultiplier comprises a trans-impedance amplifier, a plurality of resistors connected in parallel, an analog-to-digital converter and a controller, the first end of each resistor is connected with the inverted input end of the transimpedance amplifier, and the second end of each resistor is connected with the output end of the transimpedance amplifier; an analog switch is arranged between the first end of each resistor and the inverted input end of the transimpedance amplifier; the inverted input end of the trans-impedance amplifier is connected with the silicon photomultiplier; the output end of the transimpedance amplifier is connected with the input end of the analog-to-digital converter; the output end of the analog-to-digital converter is connected with the controller, the controller is connected with the control end of the analog switch, and the controller is used for obtaining the current value of the silicon photomultiplier according to the output value of the analog-to-digital converter. According to the invention, the current test range of the silicon photomultiplier can be improved, and high-precision current value detection is realized.

Description

Technical Field

[0001] The present application relates to the field of photoelectric testing technology, and in particular to a current testing device for a silicon photomultiplier tube. Background Art

[0002] Silicon photomultiplier (SIPM) is a photoelectric conversion device that utilizes the single-photon avalanche multiplication effect. It has the advantages of high sensitivity, low noise, fast response, and low power consumption. It is widely used in biomedicine, environmental monitoring, security and other fields.

[0003] In the current test process of silicon photomultiplier tube, a single resistor transimpedance amplifier is usually used to measure the current value of silicon photomultiplier tube. However, the current span of silicon photomultiplier tube under different bias voltages, different light intensities and different temperatures is relatively large, and the current value of silicon photomultiplier tube cannot be accurately detected using a single resistor transimpedance amplifier.

[0004] Therefore, how to improve the current test range of silicon photomultiplier tubes and achieve high-precision current value detection is a technical problem that those skilled in the art currently need to solve. Utility Model Content

[0005] The purpose of the present application is to provide a current testing device for a silicon photomultiplier tube, which can improve the current testing range of the silicon photomultiplier tube and achieve high-precision current value detection.

[0006] In order to solve the above technical problems, the present application provides a current testing device for a silicon photomultiplier tube, comprising: a transimpedance amplifier, a plurality of resistors connected in parallel, an analog-to-digital converter and a controller;

[0007] The first end of each resistor is connected to the inverting input end of the transimpedance amplifier, and the second end of each resistor is connected to the output end of the transimpedance amplifier; an analog switch is provided between the first end of each resistor and the inverting input end of the transimpedance amplifier;

[0008] The inverting input terminal of the transimpedance amplifier is connected to the silicon photomultiplier tube;

[0009] The output end of the transimpedance amplifier is connected to the input end of the analog-to-digital converter;

[0010] The output end of the analog-to-digital converter is connected to the controller, and the controller is connected to the control end of the analog switch. The controller is used to obtain the current value of the silicon photomultiplier tube according to the output value of the analog-to-digital converter.

[0011] Optionally, the resistance value of the (i+1)th resistor in the current testing device is 10 times the resistance value of the (i)th resistor.

[0012] Optionally, the non-inverting input terminal of the transimpedance amplifier is grounded.

[0013] Optionally, a voltage of +5V is connected to the positive power supply terminal of the transimpedance amplifier, and a voltage of -5V is connected to the negative power supply terminal of the transimpedance amplifier.

[0014] Optionally, the current testing device includes n analog switches, and the number of analog switches in the on state at the same time is less than or equal to 1.

[0015] Optionally, the controller is used to control the analog switch corresponding to the resistor with the smallest resistance value to be turned on in an initial state.

[0016] Optionally, the analog-to-digital converter is an analog-to-digital converter with a sampling bit number greater than or equal to 12.

[0017] Optionally, the controller is a field programmable gate array.

[0018] Optionally, the controller is a micro control unit.

[0019] Optionally, the transimpedance amplifier, the resistor, the analog-to-digital converter and the controller are arranged on a printed circuit board.

[0020] The present application provides a current testing device for a silicon photomultiplier tube, comprising: a transimpedance amplifier, a plurality of resistors connected in parallel, an analog-to-digital converter and a controller; the first end of each resistor is connected to the inverting input end of the transimpedance amplifier, and the second end of each resistor is connected to the output end of the transimpedance amplifier; an analog switch is provided between the first end of each resistor and the inverting input end of the transimpedance amplifier; the inverting input end of the transimpedance amplifier is connected to the silicon photomultiplier tube; the output end of the transimpedance amplifier is connected to the input end of the analog-to-digital converter; the output end of the analog-to-digital converter is connected to the controller, the controller is connected to the control end of the analog switch, and the controller is used to obtain the current value of the silicon photomultiplier tube according to the output value of the analog-to-digital converter.

[0021] The present application connects multiple parallel resistors to the inverting input terminal of the transimpedance amplifier, and an analog switch is provided between each resistor and the inverting input terminal of the transimpedance amplifier. The controller is connected to the control terminal of the analog switch, and the value of the connected resistance can be controlled. The output terminal of the above-mentioned transimpedance amplifier is connected to the analog-to-digital converter, and the analog-to-digital converter is connected to the controller; the controller can calculate the current value of the silicon photomultiplier tube according to the output value of the analog-to-digital converter. The above scheme can flexibly select the connected resistor under different test conditions and then adjust the input impedance to adapt to different ranges of current test requirements. Therefore, the present application can improve the current test range of the silicon photomultiplier tube and achieve high-precision current value detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0023] Figure 1 A schematic structural diagram of a current testing device for a silicon photomultiplier tube provided in an embodiment of the present application;

[0024] Figure 2 A simulation diagram of a current testing device provided in an embodiment of the present application;

[0025] Figure 3 A schematic diagram of a current testing device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0026] The core of the present application is to provide a current testing device for a silicon photomultiplier tube, which can improve the current testing range of the silicon photomultiplier tube and achieve high-precision current value detection.

[0027] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] See below Figure 1 , Figure 1 A schematic structural diagram of a current testing device for a silicon photomultiplier tube provided in an embodiment of the present application.

[0029] The current testing device may include: a transimpedance amplifier 101, a plurality of parallel resistors 102, an analog-to-digital converter 103, and a controller 104;

[0030] The first end of each resistor 102 is connected to the inverting input end of the transimpedance amplifier 101, and the second end of each resistor 102 is connected to the output end of the transimpedance amplifier 102; an analog switch K is provided between the first end of each resistor 102 and the inverting input end of the transimpedance amplifier 101;

[0031] The inverting input terminal of the transimpedance amplifier 101 is connected to the silicon photomultiplier tube SIPM;

[0032] The output end of the transimpedance amplifier 101 is connected to the input end of the analog-to-digital converter 103;

[0033] The output end of the analog-to-digital converter 103 is connected to the controller 104 , and the controller 104 is connected to the control end of the analog switch K. The controller 104 is used to obtain the current value of the silicon photomultiplier tube according to the output value of the analog-to-digital converter 103 .

[0034] The controller 104 is connected to the control end of the analog switch K, so as to control each analog switch K to be turned on or off, so that a specific resistor is connected to the transimpedance amplifier 101. The output value of the analog-to-digital converter 103 is a voltage signal, and the controller 104 can control the on or off of each analog switch K according to the output value of the analog-to-digital converter 103. The controller 104 can perform calculations based on Ohm's law according to the resistance value of the turned-on resistor and the output value of the analog-to-digital converter 103 to obtain the current value of the silicon photomultiplier tube.

[0035] In this embodiment, a plurality of parallel resistors are connected to the inverting input terminal of the transimpedance amplifier, and an analog switch is provided between each resistor and the inverting input terminal of the transimpedance amplifier. The controller is connected to the control terminal of the analog switch, and can control the value of the connected resistor. The output terminal of the above-mentioned transimpedance amplifier is connected to the analog-to-digital converter, and the analog-to-digital converter is connected to the controller; the controller can calculate the current value of the silicon photomultiplier tube according to the output value of the analog-to-digital converter. The above scheme can flexibly select the connected resistor and adjust the input impedance under different test conditions to adapt to different ranges of current test requirements. Therefore, this embodiment can improve the current test range of the silicon photomultiplier tube and achieve high-precision current value detection.

[0036] As for Figure 1Further introduction to the corresponding embodiment, the above-mentioned current testing device includes n resistors, n>1, the resistance value of the i+1th resistor in the current testing device is 10 times the resistance value of the i-th resistor, 1≤i<n. Correspondingly, the current testing device includes n analog switches, and the number of analog switches in the on state at the same time is less than or equal to 1.

[0037] Specifically, the controller is used to control the analog switch corresponding to the resistor with the smallest resistance value to be turned on in the initial state. The initial state is the state of starting to use the current test device to detect the current value of the silicon photomultiplier tube. The process of using the current test device to detect the current value of the silicon photomultiplier tube includes the following steps:

[0038] Step 1: Set i=1;

[0039] Step 2: Control the analog switch corresponding to the i-th resistor to be turned on, and control the analog switches of other resistors to be turned off;

[0040] Step 3: Get the output value of the analog-to-digital converter;

[0041] Step 4: Determine whether the output value of the analog-to-digital converter is close to the maximum value (such as 95% of the maximum value); if so, add 1 to the value of i and go to step 2; if not, calculate the current value of the silicon photomultiplier tube based on the output value of the analog-to-digital converter and the resistance value of the i-th resistor.

[0042] As for Figure 1 Further introduction to the corresponding embodiment, the non-inverting input terminal of the transimpedance amplifier is grounded. The positive power supply terminal of the transimpedance amplifier is connected to a voltage of +5v, and the negative power supply terminal of the transimpedance amplifier is connected to a voltage of -5v. In other words, the positive power supply terminal of the transimpedance amplifier is connected to the first power supply, the negative power supply terminal of the transimpedance amplifier is connected to the second power supply, the output voltage of the first power supply is +5V, and the output voltage of the second power supply is -5V.

[0043] As for Figure 1 As a further introduction to the corresponding embodiment, the analog-to-digital converter is an analog-to-digital converter with a sampling bit number greater than or equal to 12.

[0044] As for Figure 1 For further introduction to the corresponding embodiment, the controller is a field programmable gate array FPGA or a micro control unit MCU.

[0045] As for Figure 1 According to a further description of the corresponding embodiment, the transimpedance amplifier, resistor, analog-to-digital converter and controller are arranged on a printed circuit board.

[0046] The process described in the above embodiment is explained below through an embodiment in actual application.

[0047] The common solution for converting the current of silicon photomultiplier tubes into voltage is implemented based on transimpedance amplifiers. Transimpedance amplifiers have the characteristics of high bandwidth, high gain, high input impedance, and low noise; however, in the FT test (Functional Test) of silicon photomultiplier tubes, the current span under different bias voltages, different light intensities, and different temperatures is relatively large, and the current size is usually in the range of 10nA-20mA. The current is converted into a voltage signal by the transimpedance amplifier of the silicon photomultiplier tube through the current signal of the silicon photomultiplier tube, and the formula is: Vout = IG1 * R11. Vout represents the output value of the analog-to-digital converter (that is, the voltage across the resistor), and R11 represents the resistance value of the resistor. When the current IG1 is 1uA, due to the high input impedance of the op amp, the current will flow through the resistor R11 to the output end Vout = 1uA * 1000Ω = 1mV; at this time, the 1mV voltage signal is easily collected by sampling the amplified analog-to-digital converter ADC. When R11 is unchanged and the current is 20mA, Vout = 20mA*1000Ω = 20V, which obviously exceeds the voltage of the conventional op amp of 5V; when R11 is unchanged and the current is 10nA, Vout = 10nA*1000Ω = 10uV, and the voltage of 10uV is difficult to separate from the thermal noise of the resistor; even if a high-gain amplifier is added later to amplify it 1000 times, when the current is at the mA level, the current amplification will exceed the transimpedance range. In summary, it is difficult to implement the FT current test of the silicon photomultiplier tube using only one resistor, because the transimpedance amplifier with a single resistor cannot cover the current test in the range of 10nA-20mA.

[0048] To solve the above technical problems, this embodiment provides a range adaptive solution for silicon photomultiplier tube FT current testing, see Figure 2 , Figure 2A simulation diagram of a current test device provided in an embodiment of the present application, in which IG1 represents the current value of the silicon photomultiplier tube, SW-SPST1, SW-SPST2, SW-SPST3 and SW-SPST4 represent analog switches, R1 and R3 represent the internal resistance of the transimpedance amplifier, R2, R9, R8 and R6 represent the resistance that can be connected to the transimpedance amplifier OPA858 (i.e., the parallel resistance described above), Vout_1 represents the voltage at the output end of the transimpedance amplifier, Vcc represents the positive power supply, and Vee represents the negative power supply. The resistance value of resistor R2 is 300Ω, the resistance value of resistor R9 is 3kΩ, the resistance value of resistor R8 is 30kΩ, and the resistance value of resistor R6 is 300kΩ. When only analog switch SW-SPST1 is turned on and the other analog switches are turned off, the current value that can be detected ranges from 10nA to 1μA; when only analog switch SW-SPST2 is turned on and the other analog switches are turned off, the current value that can be detected ranges from 1 to 100μA; when only analog switch SW-SPST3 is turned on and the other analog switches are turned off, the current value that can be detected ranges from 10 to 1000μA; when only analog switch SW-SPST4 is turned on and the other analog switches are turned off, the current value that can be detected ranges from 1 to 10mA. Figure 3 , Figure 3 This is a schematic diagram of a current testing device provided in an embodiment of the present application, which shows a power supply, a bias voltage VBIAS, a silicon photomultiplier tube, a transimpedance amplifier, an analog switch MUX, resistors R1 to R4, an analog-to-digital converter ADC, a field programmable gate array FPGA or a microcontroller unit MCU, and a ground point GND.

[0049] This solution uses a TIA transimpedance amplifier to achieve IV (current-voltage) conversion of weak currents, and uses an analog switch to select different resistors to amplify different currents; the input impedance of the amplifier is large and will not affect the pulse current signal.

[0050] When the current is 10nA, the resistance gear can be selected as 1MΩ so that the converted voltage is 10mV; when the current is 20mA, the resistance gear can be selected as 100Ω so that the converted voltage is 2V. In this solution, a field programmable logic gate array FPGA or a microcontroller unit MCU is used to generate a control signal to control the analog switch to achieve gear selection. The sampling bit number of the analog-to-digital converter can be more than 12 bits; the voltage resolution of a 12-bit / 3.3V ADC is: reference voltage / (2 12)=3.3V / 4096=0.805mV can meet the current sampling resolution. The input current of the operational amplifier is zero, and the input impedance of the operational amplifier is very high, so the current IS from the silicon photomultiplier tube selects the resistance gear of the analog switch. For example, 10nA current selects 1M resistance gear, and the converted voltage = IS*R=10nA*1MΩ=10mV; when the current reaches 20mA, the voltage = 20mA*100Ω=2V.

[0051] In this scheme, due to the presence of the transimpedance amplifier, the input impedance is very large, which has almost no effect on the original signal; the presence of the analog switch can select a suitable resistor to amplify the tiny current to mV and V levels, which improves the current measurement accuracy and sampling range. The peripheral core components are only op amps plus multi-channel analog switches, and the remaining are only conventional resistors and capacitors. There is no need for large-size sampling resistors, and the PCB layout area is also reduced. The principle of dynamic measurement of the range in this embodiment is as follows: During the actual measurement of the silicon photomultiplier tube, for safety reasons, the voltage generated by the current signal after transimpedance amplification cannot exceed the power supply voltage of the transimpedance amplifier, and the controller has certain order requirements for the resistance switching of different gears. Because the current size is unknown, it should be selected from the smallest minimum resistance gear to read the converted voltage size under different gears. When the voltage is within the voltage range after transimpedance amplification (the converted voltage size is within the range of 0 to the transimpedance power supply voltage, and the amplitude is greater than 100mV, and 100mV can avoid the sampling error caused by noise), it is a suitable gear. At this time, the ADC voltage read divided by the resistance value of the corresponding gear is equal to the current of the measured silicon photomultiplier tube SIPM at this time.

[0052] This embodiment expands the transimpedance amplifier gain by adding a controller and an analog switch to achieve current testing with a wide dynamic range.

[0053] Because the situation is complicated and cannot be listed one by one for explanation, those skilled in the art should be aware that there may be many examples based on the basic principles provided by this application combined with actual conditions, and all of them should be within the scope of protection of this application without sufficient creative work.

[0054] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0055] Specific examples are used herein to illustrate the principles and implementation methods of the present application, and the description of the above embodiments is only used to help understand the scheme and its core ideas of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A current test device for a silicon photomultiplier tube, characterized in that: include: transimpedance amplifier, multiple resistors in parallel, analog-to-digital converter, and controller; The first end of each resistor is connected to the inverting input end of the transimpedance amplifier, and the second end of each resistor is connected to the output end of the transimpedance amplifier; an analog switch is provided between the first end of each resistor and the inverting input end of the transimpedance amplifier; The inverting input terminal of the transimpedance amplifier is connected to the silicon photomultiplier tube; The output end of the transimpedance amplifier is connected to the input end of the analog-to-digital converter; The output end of the analog-to-digital converter is connected to the controller, and the controller is connected to the control end of the analog switch. The controller is used to obtain the current value of the silicon photomultiplier tube according to the output value of the analog-to-digital converter.

2. The current testing device for silicon photomultiplier tube according to claim 1, characterized in that: The resistance value of the (i+1)th resistor in the current testing device is 10 times the resistance value of the (i)th resistor.

3. The current testing device for silicon photomultiplier tube according to claim 1, characterized in that: The non-inverting input terminal of the transimpedance amplifier is grounded.

4. The current testing device for silicon photomultiplier tube according to claim 1, characterized in that: A +5V voltage is connected to the positive power supply terminal of the transimpedance amplifier, and a -5V voltage is connected to the negative power supply terminal of the transimpedance amplifier.

5. The current testing device for silicon photomultiplier tube according to claim 1, characterized in that: The current testing device includes n analog switches, and the number of analog switches in a conducting state at the same time is less than or equal to 1.

6. The current testing device for silicon photomultiplier tube according to claim 1, characterized in that: The controller is used to control the analog switch corresponding to the resistor with the smallest resistance value to be turned on in the initial state.

7. The current testing device for silicon photomultiplier tube according to claim 1, characterized in that: The analog-to-digital converter is an analog-to-digital converter with a sampling bit number greater than or equal to 12.

8. The current testing device for silicon photomultiplier tube according to claim 1, characterized in that: The controller is a field programmable logic gate array.

9. The current testing device for silicon photomultiplier tube according to claim 1, characterized in that: The controller is a micro control unit.

10. The current testing device for silicon photomultiplier tube according to claim 1, characterized in that: The transimpedance amplifier, the resistor, the analog-to-digital converter and the controller are arranged on a printed circuit board.

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