一种静电计运算放大器测试电路设计

A Test Circuit Design of Electrometer Operational Amplifier

为提高直流微电流测量的准确度,对测量原理电路的噪声进行分析,确定不同噪声对直流微电流测量的影响,选定低噪声测量原则。对测量结果误差进行分析,得到电路中反馈电阻最大允许误差、运算放大器的输入偏置电流、失调电压为主要影响因素,并根据实际元器件进行举例分析验证。静电计运算放大器对测量误差的影响仍不可忽略,设计电路测量其关键指标,针对微弱电流信号的特点采取屏蔽、保护措施,搭建测试电路,测试筛选出低输入偏置电流、低失调电压的静电计运算放大器应用在高精度源表中。

In order to improve the accuracy of DC micro⁃current measurement,the noise of measuring principle circuit is analyzed,the influence of different noise on DC micro⁃current measurement is determined,and the principle of low noise measurement is selected.The error of the measurement results is analyzed,and the maximum allowable error of the feedback resistance,the input bias current of the operational amplifier and the offset voltage are the main influencing factors.The examples are analyzed and verified according to the actual components.The influence of the electrometer operational amplifier on the measurement error can not be ignored.The circuit is designed to measure its key indicators.According to the characteristics of the weak current signal,shielding and protection measures are taken,the test circuit is built,and the electrometer operational amplifier with low input bias current and low offset voltage is tested and selected for application in the high⁃precision source meter.