β对称性对差分电路共模抑制比的影响

The Impact of Symmetry on Common-Mode Rejection Ratio for Differential Circuits

本文分析了差分放大电路三极管电流放大倍数β对称性对共模抑制比的影响,通过仿真获得了单端、双端输出的对称性与共模抑制比的关系。仿真表明,共模抑制比随着对称性变差会降低。5组电路的测试结果和仿真一致。本文对学生理解差分放大电路和共模抑制比有指导意义。

This paper analyzed the impact of the transistor symmetry on the common-mode rejection ratio (CMRR) of differential amplifier. Through calculation the relationship between transistor symmetry and CMRR is obtained both in single-ended output and double-ended output. Simulation results show that the CMRR decreases as the transistor symmetry deteriorates. Experiments are carried out on the 5 groups of transistors. The results consistent with the simulation. The analysis can help students understand the principle of CMRR and the differential amplifier circuit.