The general formulations of relative variance for negative amplifier were deduced under condition that feedback coefficient was changing,the block schematic diagram analysis method was used for negative feedback amplifier with voltage parallel connection,and the differential,deviation and the general formulation for the circuits were discussed.The results indicated that the solutions for types of dif ferential and deviation were almost identical with little changing of gain（ΔA）,only the deduced formulation was confirmed when the feedback coefficient was changed,and the three formulations were in large difference when gain（ΔA） was large simultaneously.The results also display that the general formulation of relative variance has universal significance.%推导反馈系数改变条件下的负反馈放大器增益相对变化量的一般公式.对电压并联负反馈放大电路采用方框图分析法,以微分形式、差分形式,以及一般公式对其相对变化量进行讨论.结果表明：基本放大器增益变化ΔA不大时,微分形式与差分形式计算结果基本一致;反馈系数改变时,仅有所推的一般公式成立;若同时ΔA也较大,3个公式的结果可以相差很大,说明相对变化量的一般公式具有普遍意义.
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