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Low-impedance long-wave infrared detectors (the wavelength longer than 10 microns) have very important applications in cryogenic aim detection, super-distance detection, anti-jamming target identify and so on. Therefore the research in the field of infrared detector technology is of importance. At present, no low-impedance photoconductive detectors are integrated with CMOS circuit. To design low-temperature CMOS circuit being fit for low impedance infrared photoconductive detector and realize high performance IR imaging, using differential amplifier with symmetrical positive and negative power is necessary, the low-resist detector is connected between an input and grounding, the corresponding low resistance is connected between another input and grounding, a larger feedback resistor is used between negative input and output, this structure can effectively solve the matching problem of low-impedance and high-impedance CMOS. In addition, the noise voltage from VBIAS terminal can be effectively reduced by increasing the ratio of the bias resistor and the detector resistance. The whole circuit is designed two grade. The first grade is adopted bridge input structure, this structure is fit for low impedance detector. The positive amplifying method is applied in second grade . The first grade feedback resistance is designed 1M ohm, the circuit is supplied by ±1.5V. The testing showed that the circuit can work well when it connects with low-impedance infrared photoconductive detector at the liquid nitrogen low temperature. The magnification is up to 30000 times, 3dB bandwidth is more than 4kHz, the equivalent input noise is near 1.5 micron volts. This circuit has perfectly solved the matching problem between high impedance CMOS circuit and low impedance detector.
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