In order to improve the accuracy of infrared detectors to detect the infrared weak signal, a preamplifier circuit was built with a constant current bias circuit and a low-noise high-speed operational amplifier. The equivalent noisy model was deduced based on the circuit theory. The output voltage noise of the 1st amplification circuit was calculated with the superposition method. In temperature blackbody furnace experiment, the circuit performance was tested, the voltage waveform at 500℃ ~ 700℃ was obtained, and signal-to-noise ratio of 7. 25 × 10 was obtained. The results show that the preamplifier circuit of infrared detection achieves the application goal of high signal-to-noise ratio, response speed and strong anti-jamming performance, it can be used to amplify the weak infrared signal.%为了提高红外探测器检测红外微弱信号的精度,采用晶体管恒流偏置电路,使用低噪声高速运算放大器构成了前置放大电路.运用电路理论建立放大电路的噪声等效模型,采用叠加法计算1级放大输出端的噪声电压.通过中温黑体炉红外辐射实验,测试电路性能,取得了500℃ ～ 700℃时的电压波形,计算得出信噪比为7.25×103.结果表明,红外探测器前置放大电路达到高信噪比、响应速率快、抗干扰强的应用要求,可以对红外微弱信号检测放大.
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