分压式偏置共射极放大电路怎么计算

推荐回答

(1)、UBQ = Ucc - RB1( IBQ + UBQ/RB2 )，( 1 + 3 )UBQ = 12 - 60IBQ，UBQ = 3 - 15IBQ；

且，UBQ = UBEQ + ( 1 + β )IBQ * RE = 0.7 + 51 * 2IBQ；

故 3 - 15IBQ = 0.7 + 102IBQ，  117IBQ = 2.3， IBQ = 0.02 mA；

UBQ = 3 - 15 * 0.02 = 2.7 v；

ICQ = βIBQ = 50 * 0.02 = 1 mA；

UCEQ = Ucc - Rc * ICQ - UEQ = 12 - 3 * 1 - ( 2.7 - 0.7 ) = 7 v；

(2)、reb = 300 + 26/IBQ = 300 + 26/0.02 = 1600 Ω；

Ri = reb//RB1//RB2 = 1.6//60//20 = 1.446 kΩ；

ib = ui/reb = ui/1.6 mA；ic = βib = 50ui/1.6 mA；

Ro = RC//RL = 2//3 = 1.2 kΩ；

uo = icRo = 50ui/1.6 * 1.2 = 150ui/4；

AU = uo/ui = (150ui/4)/ui = 37.5 。

若RB1虚焊，基极无正向偏压，三极管截止，放大电路失效 。