非理想运放增益误差的MathCAD定量分析

摘要

在推导非理想运算放大器增益误差表达式的基础上,利用MathCAD分析讨论运算放大器的非理想参数开环增益、输入和输出电阻对实际增益误差的影响,对比现代实际运放与理想运放的差别.结果表明:运放的差模输入电阻和输出电阻对增益误差的影响较小,而开环增益是主要影响因素.开环增益越大,误差越小;目标增益较小,增益误差也较小.对现代运放而言,反馈电阻可以有很大的取值范围,基本不受运放非理想参数的限制.%On the base of formulating the expression of gain error, the author utilize MathCAD to analyze the real gain error under the influence of nonideal parameters of operational amplifier which include the open-loop gain, input resistance and output resistance and compare the difference between the real operational amplifiers and the ideal ones. The results show:the input and output resistance have minor influence on the gain error,while the open-loop gain is the main factor: the bigger the open-loop gain is, the smaller the gain error is. It has also been proved that minor error can be obtained when the target gain is minor. As for the modern operational amplifier, the value of the feedback resistance can be settled in a wide range and it is hardly restricted by the nonideal parameters.