A mercury cadmium telluride detector with a low temperature preamplifier circuit

Abstract

The application relates to a tellurium cadmium mercury detector with a low-temperature preamplifier circuit, which comprises an indium sheet, an aluminum nitride ceramic circuit board, low-temperature glue, a tellurium cadmium mercury detector and a platinum resistance on a dewar cold head in sequence; the aluminum nitride ceramic circuit board is provided with a low-temperature preamplifier circuit, the amplifier circuit comprises two bias branches for setting a bias current for the detector, four channels of feedback loops which can be externally gated for setting an amplification gain, a positive feedback loop for adjusting the nonlinearity of an output signal under strong light, and a series of resistance for inhibiting the oscillation of the amplifier circuit at low temperature. The detector and the preamplifier circuit are closely interconnected and work in a low-temperature environment, so that the electromagnetic interference coupled into the circuit loop can be effectively reduced; when working, the detector is placed in a metal dewar, and the metal shell of the dewar can shield the electromagnetic interference from the outside, so that the influence of the electromagnetic interference on the amplifier circuit can be further reduced, and the overall signal-to-noise ratio can be effectively improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of tellurium-cadmium-mercury detectors, and relates to a tellurium-cadmium-mercury detector with a low-temperature preamplification circuit. BACKGROUND

[0002] The tellurium-cadmium-mercury detector is widely applied in forest fire prevention, train hot axle monitoring, safety protection and the like due to the advantages of adjustable response spectrum, high response rate, low noise and fast response speed.

[0003] Since the tellurium-cadmium-mercury detector needs to work in a low-temperature environment, the typical temperature is 77K, in many application scenarios such as field operation, in order to improve the portability of the infrared detection system, a Stirling cryocooler is generally used to cool the tellurium-cadmium-mercury detector. The electromagnetic interference generated when the Stirling cryocooler is powered on and circulates greatly interferes with the amplification circuit of the detector, and limits the improvement of the signal-to-noise ratio of the whole detection system. SUMMARY

[0004] The application aims to provide a tellurium-cadmium-mercury detector with a low-temperature preamplification circuit, and solve the problem that the existing detector cannot avoid the electromagnetic interference generated when the Stirling cryocooler is powered on and circulates.

[0005] To achieve the above-mentioned purpose, the technical scheme of the application is as follows:

[0006] A tellurium-cadmium-mercury detector with a low-temperature preamplification circuit comprises a Dewar cold head, an indium sheet, a ceramic circuit board, low-temperature glue, a platinum resistance and a tellurium-cadmium-mercury detector; the Dewar cold head, the indium sheet and the ceramic circuit board are sequentially stacked and fastened;

[0007] The low-temperature glue is arranged on the ceramic circuit board, and the platinum resistance and the tellurium-cadmium-mercury detector are arranged on the low-temperature glue;

[0008] The low-temperature preamplification circuit is arranged on the ceramic circuit board, and the tellurium-cadmium-mercury detector is connected with the low-temperature preamplification circuit; the low-temperature preamplification circuit comprises a first bias branch, a second bias branch, a feedback loop with a gating switch and a positive feedback loop;

[0009] The low-temperature preamplification circuit further comprises an operational amplifier, the negative input end of the operational amplifier is connected with the first bias branch, and the positive input end is connected with the second bias branch; the negative input end of the operational amplifier is connected with a program-controlled switch, and the program-controlled switch controls the gating switch of the feedback loop through two input ends.

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

[0011] In the low-temperature preamplification circuit, the resistance R of the tellurium-cadmium-mercury detector detector is connected with the first resistance R biasThe first resistor is connected in series in the first bias branch; the second resistor R2 and the third resistor R3 are connected in series in the second bias branch, and the first capacitor C1 is connected in parallel across R3.

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

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

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

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

[0016] The advantages of this invention are: 1. The low-temperature preamplifier circuit and the mercury cadmium telluride detector chip are packaged together in a Dewar flask and operate in a low-temperature environment. The signal output after amplification by the low-temperature preamplifier has greatly enhanced anti-interference capability; 2. Due to its small circuit loop, the low-temperature preamplifier circuit receives less electromagnetic interference, 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 flask, and the metal shell of the Dewar flask can shield against external electromagnetic interference, further reducing the impact of electromagnetic interference on the amplification circuit. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the mercury cadmium telluride detector with a low-temperature preamplifier circuit according to the present invention.

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

[0019] In the diagram: 1-Dewar cold head; 2-Indium plate; 3-Ceramic circuit board; 4-Low temperature adhesive; 5-Platinum resistance thermometer; 6-Mercury cadmium telluride detector. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings. The drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0021] To simplify the description of this embodiment, some components that are well-known to those skilled in the art but are not related to the main content of this invention may be omitted in the accompanying drawings or description. Additionally, for ease of description, some components in the drawings may be omitted, enlarged, or reduced, but these do not represent the actual product dimensions or the complete structure.

[0022] The application discloses a tellurium-cadmium-mercury detector with a low-temperature preamplifier circuit. Figure 1 As shown in the figure, the tellurium-cadmium-mercury detector comprises a dewar cold head 1, an indium sheet 2, a ceramic circuit board 3, a low-temperature glue 4, a platinum resistance 5 and a tellurium-cadmium-mercury detector 6; the dewar cold head 1 has a thickness of about 10 mm and is used as a heat sink of the tellurium-cadmium-mercury detector assembly; the indium sheet 2 has a thickness of about 2 mm and is used as a heat conduction layer between the ceramic circuit board 3 and the dewar cold head 1; the ceramic circuit board 3 is made of aluminum nitride, the aluminum nitride ceramic circuit board 3 has a thickness of 1.6 mm, and a low-temperature preamplifier circuit structure is arranged on the ceramic circuit board 3.

[0023] The low-temperature glue 4 is used for bonding the tellurium-cadmium-mercury detector 6 and the platinum resistance 5; the platinum resistance 5 is a PT100 type and is used for testing the temperature near the position of the tellurium-cadmium-mercury detector 6; and the tellurium-cadmium-mercury detector 6 is used for converting an infrared waveband photoelectric signal.

[0024] The dewar cold head 1, the indium sheet 2 and the ceramic circuit board 3 are sequentially stacked and fastened; the indium sheet 2 is located between the dewar cold head 1 and the ceramic circuit board 3 and is required to be closely attached to the dewar cold head 1 and the ceramic circuit board 3 to ensure good heat conduction.

[0025] The ceramic circuit board 3 is made of aluminum nitride material, which has high thermal conductivity, so that the temperature of the tellurium-cadmium-mercury detector 6 is basically consistent with the temperature of the dewar cold head 1; the ceramic circuit board 3 is made by 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 material, because volatilization of the organic material will cause the vacuum degree in the dewar to decrease, thereby affecting the refrigeration effect.

[0026] The low-temperature preamplifier circuit is arranged on the ceramic circuit board 3, as shown in the figure, the tellurium-cadmium-mercury detector 6 is connected with the low-temperature preamplifier circuit, and the low-temperature preamplifier circuit comprises a first bias branch, a second bias branch, a feedback loop with a gating switch and a positive feedback loop. Figure 2

[0027] The low-temperature preamplifier circuit further comprises an operational amplifier, a negative input end of the operational amplifier is connected with the first bias branch, and a positive input end of the operational amplifier is connected with the second bias branch; the negative input end of the operational amplifier is connected with a program-controlled switch, and the program-controlled switch controls the gating switch of the feedback loop through two input ends.

[0028] In the low-temperature preamplifier circuit, an operational amplifier with extremely low input noise is selected, for example, an LT1028 amplifier with an input noise of 0.9 nV / Hz 1 / 2 .

[0029] In the low-temperature preamplifier circuit, the resistance R detector of the tellurium-cadmium-mercury detector 6 is connected with a first resistance R bias ​The first resistor is connected in series in the first bias branch; the 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 ratio of the first resistor R in the first bias branch. bias With resistance R detector The ratios must be the same.

[0030] A first capacitor C1 is also connected in parallel across R3; the first capacitor C1 is used to filter out high-frequency noise in the second bias branch.

[0031] A fourth resistor R4 is connected in the positive feedback loop. The fourth resistor R4 is connected to the positive input terminal and the output terminal of the operational amplifier, respectively. 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. The purpose of this resistor is 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 containing four channels, and the output terminals of the four channels are connected to the output terminals of the operational amplifier.

[0034] The negative input of the operational amplifier is connected to a programmable switch. This switch can control a selection switch through two input terminals: input 00 selects channel S1, input 01 selects S2, input 10 selects S3, and input 11 selects S4. The first channel includes a feedback resistor R. f1 With feedback capacitor C f1 The two are connected in parallel. The other channels contain corresponding feedback resistors and feedback capacitors. 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 detector The RΩ is approximately 100Ω. To ensure the mercury cadmium telluride detector 6 operates at a bias current of 1mA, with the external power supply VCC at 3.3V, R... bias R1 is set to 3.2kΩ; R2 is set to 3.2kΩ, R3 is set to 100Ω; capacitor C1 is set to 10μF.

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

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

[0038] The feedback resistor R of the first channel in the four-channel configuration 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 resistance R f2 Set to 5kΩ, C f2 Set to 30pF, the gain of the second channel is about 50 times; the feedback resistance R f3 Set to 10kΩ, C f3 Set to 30pF, the gain of the third channel is about 100 times; the feedback resistance 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, and the output signal under different scene and different incident light can be adjusted.

[0040] The whole low-temperature preamplifier circuit is made on the aluminum nitride ceramic circuit board 3, and the resistors, capacitors and operational amplifiers and other components are welded on the ceramic circuit board 3 in a surface mounting manner; the ceramic circuit board 3 is required to have high thermal conductivity to ensure that the temperature of the tellurium cadmium mercury detector 6 is basically consistent with the temperature of the dewar cold head 1;

[0041] The tellurium cadmium mercury detector 6 and the platinum resistance 5 are bonded on the ceramic circuit board 3 through the low-temperature glue 4, and the two electrodes of the tellurium cadmium mercury detector 6 are connected to the low-temperature preamplifier circuit by gold wire bonding;

[0042] The ceramic circuit board 3 and the dewar cold head 1 adopt indium sheet 2 as a transition layer, 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 time; second, the indium sheet 2 is soft, and when pressed, it can ensure that the ceramic circuit board 3 and the dewar cold head 1 are in full and close contact.

[0043] The above only describes the preferred embodiments of the present application, and is not intended to limit the scope of the application. Any equivalent changes and modifications made within the scope of the present application should be within the technical scope of the present application.

Claims

1. A tellurium cadmium mercury detector with low-temperature preamplifier circuit, comprising a dewar cold head (1), an indium sheet (2), a ceramic circuit board (3), low-temperature glue (4), a platinum resistance (5) and a tellurium cadmium mercury detector (6); the dewar cold head (1), the indium sheet (2) and the ceramic circuit board (3) are sequentially stacked and fastened; characterized in that The low-temperature glue (4) is arranged on the ceramic circuit board (3), and the platinum resistance (5) and the tellurium cadmium mercury detector (6) are arranged on the low-temperature glue (4); The low-temperature preamplifier circuit is arranged on the ceramic circuit board (3), and the tellurium cadmium mercury detector (6) is connected with the low-temperature preamplifier circuit, and the low-temperature preamplifier circuit comprises a first bias branch, a second bias branch, a feedback loop with a gating switch and a positive feedback loop; The low-temperature preamplifier circuit further comprises an operational amplifier, a negative input end of the operational amplifier is connected with the first bias branch, and a positive input end of the operational amplifier is connected with the second bias branch; the negative input end of the operational amplifier is connected with a program-controlled switch, and the program-controlled switch controls the gating switch of the feedback loop through two input ends.

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

3. The HgCdTe detector with 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 is connected in series with a first resistance R bias in a first bias branch; a second resistance R2 is connected in series with a third resistance R3 in a second bias branch, and a first capacitor C1 is connected in parallel across R3; A fourth resistance R4 is connected in the positive feedback loop, and the fourth resistance R4 is connected with the positive input end and the output end of the operational amplifier respectively; A fifth resistance R5 is connected between the output end of the operational amplifier and a signal output end.

4. The HgCdTe detector with low temperature preamplifier circuit according to claim 3, characterized in that: The feedback loop is a feedback loop comprising four channels, and output ends of the four channels are connected with the output end of the operational amplifier.

5. The HgCdTe detector with low temperature preamplifier circuit according to claim 3, characterized in that: The ratio of the second resistance R2 and the third resistance R3 in the second bias branch is the same as the ratio of the first resistance R bias and the second resistance R detector in the first bias branch.

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