s=A3=A2(r)输入串联时 s=Av=A3(-)输入并联时 电流串联电路: L +(-A2r) A B R R R gSS O 得:R==R(1+AB,) 电流并联电路: R R R O 得: R2(1+A3B)( ) s s gss d gss f i = A v = A −v 输入串联时 ( ) s s iss d iss f i = A v = A −i 输入并联时 gss r o o o gss f o o s s o o o A B i R v A v R v i R v i = + = + (− ) = − 得： (1 ) o gss r o o o f R A B i v R = = + 电流串联电路： iss i o o o iss f o o s s o o o A B i R v A v R v i R v i = + = + (− ) = − 得： (1 ) o iss i o o of R A B i v R = = + 电流并联电路：