u =TFFu2 +TFBu3 =TFFu;+TrBuo 由运放电路特性,有: u。=A(u+-u_)=-Au1 2 =-A[TFFU;+TFB。] 3 =-ATEU,-ATEEu。 RC [1+ATEB]u。=-ATFFu, 有: T=。=-ATm TFE uo 三一 Vi 1+ATrB 1 A 理想运放有: A>∞ T=一 TFE TFB由运放电路特性,有: ui uo RC 1 3 2 uo A(u u ) Au1 ATFB uo ATFFui [1 ] 有: A T T AT AT u u T FB FF FB FF i o 1 1 理想运放有: A FB FF T T T u1 TFFu2 TFBu3 TFFui TFBuo FF i FB o FF i FB o AT u AT u AT u T u [ ]