电路分析基础 2.12图示电路为晶体管放大器等效电路，电路中各电阻及β均为已知，求电流Ai.电压放大系数Au

Question

（Ai=i2/i1，Au=u2/Us)

Answer 1

Rbe也应该为已知。
(1) us=ib*Rbe+(β+1)ib*RF
u2=βib*（RL//Rc）
Au=u2/us=β (RL//Rc)/(Rbe+(β+1)*RF)
特别地：当β >>1、Rbe<<βRf时
Au=(RL//Rc)/Rf
(2) i2=βib*(Rc/(RL+Rc))
i1=ib+(ib*Rbe+(β+1)ib*RF)/Rb=ib(1+(Rbe+(β+1)Rf)/Rb)
Ai=(β*(Rc/(RL+Rc)))/(1+(Rbe+(β+1)Rf)/Rb))
特别地：当β >>1、Rbe<<βRf时、Rb<<(β+1)Rf时
Ai=(Rb/Rf)*(Rc/(RL+Rc))本回答被提问者和网友采纳

Answer 2

Au=β×Rc/Rbe套公式就行

Answer 3

Us=ib*(Rbe+(1+β)Rf);
I1=Us/(Rb//(Rbe+(1+β)Rf));
U2=-βib *(Rc//RL);
I2=U2/RL;
AI=I2/I1= U2/RL/ Us/(Rb//(Rbe+(1+β)Rf))= -β(Rc//RL){ Rb//[Rbe+(1+β)Rf]} / { RL [Rbe+(1+β)Rf)};
AU=U2/US=-βib *(Rc//RL) / ib*(Rbe+(1+β)Rf)= -β(Rc//RL) /(Rbe+(1+β)Rf);
然后自己再化简一下就可以了~~