R1 R R R 2 B1△iB △ lBl R RL R R1 T u △ulo B2△i32 差模放大倍数A1 △ R B(R。∥ △ △iB·2(Rb+) R,+ R=2(R, +re Od △ic·2(R∥-) R=2R) 2 2( 2( ) L Od C c Id B b be Id Od d R u i R u i R r u u A ∥ 差模放大倍数  = −   =   +   = 2 2( ) ) 2 ( o c i b be b be L c d R R R R r R r R R A = = + + = −  ∥