在测量交流高阻平衡网路(电桥和补偿器)中,当输出阻抗Z出>10~5欧姆时,为扩大量限和提高其测量准确度,需要创制一种灵敏的指零仪。一般工厂所生产的指零仪的灵敏度约为(0.5—1)·10~(-6),输入阻抗约0.5兆欧和分布电容30微微法(如—7,φ510,φ550),其性能不能满足实际要求。本文所介绍的高灵敏度选频放大器是在交 In the measurement of AC high impedance balanced network (bridge and compensator), when the output impedance Z> 10 ~ 5 ohms, in order to expand the quantum limit and improve the measurement accuracy, the need to create a sensitive zero instrument. General factory production zero finger instrument sensitivity of about (0.5-1) 10 ~ (-6), the input impedance of about 0.5 megaohms and distributed capacitance 30 pico-method (such as -7, φ510, φ550), the performance can not Meet the actual requirements. This article describes the high-sensitivity frequency-selective amplifier is to pay