由单环反馈的理想方块图知: X。(S)=A(s)ka(S) X(s)=X(3)-Xr(s) X (s=B(SX(s) 反馈放大电路的闭环增益为: A,(s) A(s) X1(s)1+A(s)B(s)X (s) A(s)X (s) o = d X (s) X (s) X (s) d = i − f X (s) B(s)X (s) f = o 由单环反馈的理想方块图知： 反馈放大电路的闭环增益为： 1 ( ) ( ) ( ) ( ) ( ) ( ) A s B s A s X s X s A s i o f + = =