kn kn 1 Mn kn 解(1)两级放大电路的电压增益 rbe3+(+B) R RpI rba3+(1+B) BRcs rbe3+(1+B) 20×12 =-4×5.1× 25+(1+20)×0.2 =730 (2)输入电阻Ra=R1‖rs≈R1=5.M2 输出电阻Rn=R3+Ra=24kC2 (3)第一级单端输出时的差模电压增益 AyDI =-gmR LI R R,+ 4×5.1=-10.2 T1、T2源极恒流源交流等效电阻解 （1）两级放大电路的电压增益 730 2.5 (1 20) 0.2 20 12 4 5.1 2 (1 ) 2 || (1 ) 2 2 (1 ) 2 3 2 3 3 1 1 2 3 ' 3 1 2 1 =       + +   = −   −             + + −               + +         = − +             + + =  = − − p b e p c b e p m d p b e c V D V V m L R r R R r R g R R r R A A A g R      （2）输入电阻 Rid = R1 || rgs  R1 = 5.1M 输出电阻 Ro = Rc3 + Rc4 = 24k （3）第一级单端输出时的差模电压增益 4 5.1 10.2 2 1 2 R || r (1 ) 2 R g R 2 1 g R 2 1 A p2 be3 p1 m d1 L1 ' VD1 m = −   = −               + +          = − + = − T1、T2 源极恒流源交流等效电阻