Aimed at active weak IR detection, how to get the stable high gain from Avalanche Photodiode (APD) circuits and its opto-electronic matching characters are researched. The methods are relation with APD exponent gain and linear noise with its reverse bias voltage. It gets closed to temperature coefficient by serial Zener diodes and always-stable bias voltage to APD near break voltage at real PN junction temperature, and is over 100 times gain with temperature complement circuits. Transistor cut-off frequency and its response are increased by NPN type transistor with an improved a.c. couple low noise and low voltage supplier negative feedback circuits. The system voltage gain enhances 2 to 3 times,and opto-electronic sensitivity rises over 23 dB. Because PN junction temperature of power LD changes causes wavelength drift, it is very difficult to match extremely narrow bandwidth interference filters. So the interference filter bandwidth between 10 and 15 nm is available for background radiation depression.<英文关键词>Avalanche Photodiode/APD; low noise amplifier circuit; temperature complement circuit; narrow bandwidth interference filter; IR background radiation