HgCdTe detector with low-temperature pre-amplification circuit

Abstract

The invention relates to a tellurium-cadmium-mercury detector with a low-temperature pre-amplification circuit. An indium sheet, an aluminum nitride ceramic circuit board, low-temperature glue, the tellurium-cadmium-mercury detector and a platinum resistor are sequentially arranged on a Dewar cold head; a low-temperature pre-amplification circuit is arranged on the aluminum nitride ceramic circuit board and comprises two bias branches, a feedback loop used for setting bias current for the detector, four channels capable of being externally gated, a positive feedback loop used for setting amplification gain, a series resistor, a low-temperature resistor, a low-temperature resistor, a low-temperature resistor, a low-temperature resistor, a high-temperature resistor and a low-temperature resistor, wherein the positive feedback loop is used for adjusting nonlinearity of an output signal under strong illumination; therefore, oscillation of the amplifying circuit at low temperature is suppressed. The detector and the pre-amplification circuit are closely interconnected, and electromagnetic interference coupled into a circuit loop can be effectively reduced when the detector works in a low-temperature environment; when working, the circuit is arranged in a metal Dewar, and the metal shell of the Dewar can shield external electromagnetic interference, so that the influence of the electromagnetic interference on the amplification circuit can be further reduced, and the overall signal-to-noise ratio is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of mercury cadmium telluride detectors, in particular to a mercury cadmium telluride detector with a low-temperature preamplifier circuit. Background Art

[0002] Mercury cadmium telluride detectors are widely used in forest fire prevention, train hot axle monitoring, safety protection and other fields due to their advantages such as adjustable response spectrum, high response rate, low noise and fast response speed.

[0003] Since HgCdTe detectors need to work in a low temperature environment, the typical temperature is 77K. In many application scenarios, such as field operations, in order to improve the portability of infrared detection systems, Stirling refrigerators are generally used to cool HgCdTe detectors. The electromagnetic interference generated by the Stirling refrigerator during power-on and cycle operation greatly interferes with the detector's amplifier circuit, limiting the improvement of the signal-to-noise ratio of the entire detection system. Summary of the invention

[0004] The purpose of the present invention is to provide a mercury cadmium telluride detector with a low-temperature preamplifier circuit, which solves the problem that the existing detector cannot avoid the electromagnetic interference generated when the Stirling refrigerator is powered on and works in a cycle.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] A mercury cadmium telluride detector with a low-temperature preamplifier circuit comprises a dewar cold head, an indium sheet, a ceramic circuit board, low-temperature glue, a platinum resistor and a mercury cadmium telluride detector; the dewar cold head, the indium sheet and the ceramic circuit board are stacked and fastened in sequence;

[0007] A low-temperature glue is arranged on the ceramic circuit board, and a platinum resistor and a mercury cadmium telluride detector are arranged on the low-temperature glue;

[0008] A low-temperature preamplifier circuit is arranged on the ceramic circuit board, and the mercury cadmium telluride detector is connected to the low-temperature preamplifier circuit, and the low-temperature preamplifier circuit includes a first bias branch, a second bias branch, a feedback loop with a gate switch, and a positive feedback loop;

[0009] The low-temperature preamplifier circuit also includes an operational amplifier, the negative input terminal of the operational amplifier is connected to the first bias branch, and the positive input terminal is connected to the second bias branch; the negative input terminal of the operational amplifier is connected to a programmable switch, and the programmable switch controls the selection switch of the feedback loop through two input terminals.

[0010] The ceramic circuit board is made of aluminum nitride.

[0011] In the low temperature preamplifier circuit, the resistance R of the mercury cadmium telluride detector detector With the first resistor R biasThe second resistor R2 and the third resistor R3 are connected in series in the second bias branch, and a first capacitor C1 is also provided in parallel at both ends of R3;

[0012] A fourth resistor R4 is connected in the positive feedback loop, and the fourth resistor R4 is respectively connected to the positive input terminal and the output terminal of the operational amplifier;

[0013] A fifth resistor R5 is connected between the output terminal of the operational amplifier and the signal output terminal.

[0014] The feedback loop is a feedback loop including four channels, and output terminals of the four channels are connected to the output terminal of the operational amplifier.

[0015] The ratio of the second resistor R2 to the third resistor R3 in the second bias branch to the first resistor R bias With resistor R detector The ratio is the same.

[0016] The advantages of the present invention are: 1. The low-temperature preamplifier circuit is packaged together with the mercury cadmium telluride detector chip in a dewar and works in a low-temperature environment. The signal output after amplification by the low-temperature preamplifier has greatly enhanced anti-interference ability; 2. Since the low-temperature preamplifier circuit has a small circuit loop, less electromagnetic interference is coupled in, which can effectively improve the signal-to-noise ratio of the entire detector assembly; 3. When the detector is working, it is placed in a metal dewar, and the metal shell of the dewar can shield the external electromagnetic interference, which can further reduce the influence of electromagnetic interference on the amplifier circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a mercury cadmium telluride detector with a low-temperature preamplifier circuit of the present invention;

[0018] Figure 2 1 is a circuit diagram of a low-temperature preamplifier circuit of the present invention.

[0019] In the figure: 1-Dewar cold head; 2-Indium sheet; 3-Ceramic circuit board; 4-Low-temperature glue; 5-Platinum resistor; 6-HgCdTe detector. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with the accompanying drawings, which are only used for exemplary description and cannot be understood as limiting the present invention.

[0021] In order to more concisely describe the present embodiment, some parts known to those skilled in the art but not related to the main content of the present invention are omitted in the drawings or descriptions. In addition, for the convenience of description, some parts in the drawings are omitted, enlarged or reduced, but they do not represent the size or entire structure of the actual product.

[0022] The present invention discloses a mercury cadmium telluride detector with a low temperature preamplifier circuit, such as Figure 1 As shown, it includes a Dewar cold head 1, an indium sheet 2, a ceramic circuit board 3, a low-temperature glue 4, a platinum resistor 5 and a mercury cadmium telluride detector 6; the Dewar cold head 1, which is about 10 mm thick, is used as a heat sink for the mercury cadmium telluride detector assembly; the indium sheet 2, which is about 2 mm thick, is used as a heat conductive layer between the ceramic circuit board 3 and the Dewar cold head 1; the ceramic circuit board 3 is made of aluminum nitride, and the aluminum nitride ceramic circuit board 3 is 1.6 mm thick, and a low-temperature preamplifier circuit structure is provided on the ceramic circuit board 3.

[0023] The low temperature glue 4 is used for bonding the mercury cadmium telluride detector 6 and the platinum resistor 5; the platinum resistor 5, model PT100, is used for testing the temperature near the position of the mercury cadmium telluride detector 6; the mercury cadmium telluride detector 6 is used for photoelectric signal conversion in the infrared band.

[0024] The Dewar cold head 1, the indium sheet 2 and the ceramic circuit board 3 are stacked and fastened in sequence; the indium sheet 2 is located between the Dewar cold head 1 and the ceramic circuit board 3 and must fit tightly with both the Dewar cold head 1 and the ceramic circuit board 3 to ensure good thermal conductivity.

[0025] The ceramic circuit board 3 is made of aluminum nitride material, which has high thermal conductivity, so that the temperature of the mercury cadmium telluride detector 6 is basically consistent with the temperature of the Dewar cold head 1; the ceramic circuit board 3 is made of thick film technology, and the side in contact with the indium sheet 2 is protected by inorganic insulating glue; the ceramic circuit board 3 cannot use conventional organic solder resist materials, because the volatilization of organic materials will cause the vacuum degree in the Dewar to decrease, affecting the refrigeration effect.

[0026] A low temperature preamplifier circuit is provided on the ceramic circuit board 3, such as Figure 2 As shown, the mercury cadmium telluride detector 6 is connected to the low-temperature preamplifier circuit, and the low-temperature preamplifier circuit includes a first bias branch, a second bias branch, a feedback loop with a gate switch, and a positive feedback loop;

[0027] The low-temperature preamplifier circuit also includes an operational amplifier, the negative input terminal of the operational amplifier is connected to the first bias branch, and the positive input terminal is connected to the second bias branch; the negative input terminal of the operational amplifier is connected to a programmable switch, and the programmable switch controls the selection switch of the feedback loop through two input terminals.

[0028] In the low temperature preamplifier circuit, an operational amplifier with extremely low input noise is selected, such as 0.9nV / Hz 1 / 2 The LT1028 amplifier.

[0029] In the low temperature preamplifier circuit, the resistance R of the mercury cadmium telluride detector 6 detector With the first resistor R biasThe second resistor R2 and the third resistor R3 are connected in series in the second bias branch, and the ratio of the second resistor R2 to the third resistor R3 in the second bias branch is equal to the first resistor R bias With resistor R detector The ratios must be the same.

[0030] A first capacitor C1 is also provided in parallel with both ends of R3; the first capacitor C1 is used to filter out high-frequency noise of the second bias branch.

[0031] A fourth resistor R4 is connected in the positive feedback loop. The fourth resistor R4 is respectively connected to the positive input terminal and the output terminal of the operational amplifier. The fourth resistor R4 is connected in the positive feedback loop to adjust the nonlinearity of the signal output.

[0032] A fifth resistor R5 is connected between the output terminal of the operational amplifier and the signal output terminal, in order to adjust the phase of the feedback loop and prevent the circuit from oscillating at low temperatures.

[0033] like Figure 2 As shown, the feedback loop is a feedback loop including four channels, and the output ends of the four channels are connected to the output end of the operational amplifier.

[0034] The negative input of the operational amplifier is connected to a programmable switch, which can control the selection switch through two input terminals, that is, when the input is 00, the first channel S1 is selected, when the input is 01, S2 is selected, when the input is 10, S3 is selected, and when the input is 11, S4 is selected; the first channel contains the feedback resistor R f1 With the feedback capacitor C f1 The two are in parallel relationship, and the other channels contain corresponding feedback resistors and feedback capacitors respectively. Different feedback resistors are used to set different amplification factors of the circuit; the feedback capacitors in the four channels S1-S4 are used to adjust the phase of the amplifier circuit to prevent the circuit from oscillating at low temperatures.

[0035] The following is a specific embodiment. The resistance R of the mercury cadmium telluride detector 6 is detector is about 100Ω. In order to make the HgCdTe detector 6 work under the bias current of 1mA, when the external power supply VCC is 3.3V, R bias Set to 3.2kΩ; R2 is set to 3.2kΩ, R3 is 100Ω; capacitor C1 is set to 10μF.

[0036] The fourth resistor R4 is set to 100 kΩ to adjust the nonlinearity of the amplifier circuit when strong light is incident.

[0037] The fifth resistor R5 is set to 100Ω to suppress oscillation of the preamplifier circuit at low temperatures.

[0038] The feedback resistor R of the first channel among the four channels f1Set to 1kΩ, C f1 Set to 20pF, according to the gain formula G = 1 + R f1 / (R bias / / R detector ), the gain of the first channel is about 10 times; the feedback resistor R f2 Set to 5kΩ, C f2 Set to 30pF, the gain of the second channel is about 50 times; the feedback resistor R f3 Set to 10kΩ, C f3 Set to 30pF, the gain of the third channel is about 100 times; the feedback resistor R f4 Set to 100kΩ, C f4 Set to 50pF, the gain of the fourth channel is about 1000 times.

[0039] By selecting the external gear input level, different gain gears can be switched to amplify the detector signal, so as to adjust the output signal under different incident light in different scenes.

[0040] The entire low-temperature preamplifier circuit is made on an aluminum nitride ceramic circuit board 3, and components such as resistors, capacitors, and operational amplifiers are soldered on the ceramic circuit board 3 by surface mounting. The ceramic circuit board 3 is required to have high thermal conductivity to ensure that the temperature of the mercury cadmium telluride detector 6 is basically consistent with the temperature of the Dewar cold head 1.

[0041] The mercury cadmium telluride detector 6 and the platinum resistor 5 are bonded to the ceramic circuit board 3 by means of a low-temperature adhesive 4, and the two electrodes of the mercury cadmium telluride detector 6 are connected to the low-temperature preamplifier circuit by means of gold wire bonding;

[0042] An indium sheet 2 is used as a transition layer between the ceramic circuit board 3 and the Dewar cold head 1. The main reasons are: first, the indium sheet 2 has good thermal conductivity, which helps to transfer the heat generated by the circuit on the ceramic circuit board 3 to the Dewar cold head 1 in a timely manner; second, the indium sheet 2 is soft in texture, and when pressed tightly, it can ensure sufficient and close contact with the ceramic circuit board 3 and the Dewar cold head 1 respectively.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. That is, any equivalent changes and modifications made according to the content of the patent application scope of the present invention should be within the technical scope of the present invention.

Claims

1. A mercury cadmium telluride detector with a low-temperature preamplifier circuit, comprising a Dewar cold head (1), an indium sheet (2), a ceramic circuit board (3), a low-temperature glue (4), a platinum resistor (5) and a mercury cadmium telluride detector (6); the Dewar cold head (1), the indium sheet (2) and the ceramic circuit board (3) are stacked and fastened in sequence; Features: A low-temperature glue (4) is arranged on the ceramic circuit board (3), and a platinum resistor (5) and a mercury cadmium telluride detector (6) are arranged on the low-temperature glue (4); A low-temperature preamplifier circuit is arranged on the ceramic circuit board (3), and the mercury cadmium telluride detector (6) is connected to the low-temperature preamplifier circuit, wherein the low-temperature preamplifier circuit comprises a first bias branch, a second bias branch, a feedback loop with a gate switch, and a positive feedback loop; The low-temperature preamplifier circuit also includes an operational amplifier, the negative input terminal of the operational amplifier is connected to the first bias branch, and the positive input terminal is connected to the second bias branch; the negative input terminal of the operational amplifier is connected to a programmable switch, and the programmable switch controls the selection switch of the feedback loop through two input terminals.

2. The mercury cadmium telluride detector with a low-temperature preamplifier circuit according to claim 1, characterized in that: The ceramic circuit board (3) is made of aluminum nitride.

3. The mercury cadmium telluride detector with a low-temperature preamplifier circuit according to claim 1, characterized in that: In the low temperature preamplifier circuit, the resistance R of the mercury cadmium telluride detector (6) detector With the first resistor R bias The second resistor R2 and the third resistor R3 are connected in series in the second bias branch, and a first capacitor C1 is also provided in parallel at both ends of R3; A fourth resistor R4 is connected in the positive feedback loop, and the fourth resistor R4 is respectively connected to the positive input terminal and the output terminal of the operational amplifier; A fifth resistor R5 is connected between the output terminal of the operational amplifier and the signal output terminal.

4. The mercury cadmium telluride detector with a low-temperature preamplifier circuit according to claim 3, characterized in that: The feedback loop is a feedback loop including four channels, and output terminals of the four channels are connected to the output terminal of the operational amplifier.

5. The mercury cadmium telluride detector with a low-temperature preamplifier circuit according to claim 3, characterized in that: The ratio of the second resistor R2 to the third resistor R3 in the second bias branch to the first resistor R bias With resistor R detector The ratio is the same.

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