Abstract: 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.

Key words: Transimpedance amplifier circuit, Input bias current, Offset voltage, DC micro current detection