运放-差分电压串联负反馈的理论计算与仿真分析

The Theoretical Calculation and Simulation Analysis of Operational Amplifier-Differential voltage with Series Negative Feedback

采用方框图分析法,对所设计的直接耦合方式下的运放-差分电压串联负反馈放大电路,以多级放大增益的计算方法,计算出基本放大器的电压增益,进而由反馈放大器中的基本关系得到反馈放大器的电压增益。另外采用微变等效电路方法,将运算放大器和晶体三极管分别用电压控制电压源和电流控制电流源替代计算得到反馈放大器的电压增益,两者满足负反馈放大电路中的基本关系。同时,启用仿真软件EWB,分别测出基本放大器和反馈放大器输出电压,与输入电压做比较得电压增益,结果与理论计算最大相对误差不超过0.175%,说明方法的正确性。

By using the analysis method of block diagram and aiming at the designed operational amplifier-differential voltage amplifier circuit of the direct coupling mode with series negative feedback,the voltage gain of the basic amplifier is calculated by adopting the calculation method of multistage-amplifier gain,and then the voltage gain is obtained based on the basic relationship of the feedback amplifier.In addition,by using the small-signal equivalent circuit method,the voltage gain of the negative feedback amplifier is calculated through respectively replacing the operational amplifier and the crystal triode by voltage-controlled voltage source and current-controlled current source,both of that meet the basic relationship of negative feedback amplifier circuit.At the same time,the output voltage of the basic amplifier and the feedback amplifier are measured by using the simulation software EWB.Therefore the voltage gain is gotten by dividing the output voltage with the input voltage.By comparing the measurement results with the theoretical values,the maximum relative error is less than 0.175%.The analysis results above show that the method adopted in this paper is correct.