电压放大倍数 B Irbe sri R bI R中R L 20kT10k2 Re 2k 6k2 2k2 Icr=-BlbR Ui=lbre+ler=Ibte+(+ BRI BluR R I6Irbe +(1+B), he +(1+B)R 已:a9i b rbe i c βi b B C Rb1 E 20kΩ Rc 2kΩ RL 6kΩ Rb2 10kΩ ui Re 2kΩ 电压放大倍数 o u i U A U = o c b U I R I R = − = − L L    i b e b[ (1 ) ] U I r I R I r R = + = + + be e be e  1 1 ( ) [ ( ) ] o b L L u be e i b be e U I R R A r R U I r R       = = − = − + + + +