已知放大电路β＝50，rbb＝200Ω，UBEQ＝0.7，电路其他参数见图？50

1、IbQ = ( 12 - 0.7 )/560 = 0.02 mA；IcQ =βIbQ = 50 * 0.02 = 1 mA；UceQ = 12 - RcIcQ = 12 - 5 * 1 = 7v；2、Ri = Rb//rbe ≈ rbe = rbb + 26(mv)/IbQ = 200 + 26/0.02 = 1500Ω；Ro = Rc = 5kΩ；3、Au =βRL'/rbe =β( RL//Rc )/rbe = 50 * ( 5//5 )/1.5 = 250/3 。