基本放大电路
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静态是指无交流信号输入时,电路中的电流、电压都不变的状态,静态时三极管各极电流和电压值称为静态工作点Q(主要指IBQ、ICQ和UCEQ)。静态分析主要是确定放大电路中的静态值IBQ、ICQ和UCEQ。
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IBQ=(UCC-UBEQ)/RBICQ=βIBQUCEQ=UCC-ICQ·RC图解步骤:(1)用估算法求出基极电流IBQ(如40μA)。(2)根据IBQ在输出特性曲线中找到对应的曲线。(3)作直流负载线。根据集电极电流IC与集、射间电压UCE的关系式UCE=UCC-ICRC可画出一条直线,该直线在纵轴上的截距为UCC/RC,在横轴上的截距为UCC,其斜率为-1/ RC ,只与集电极负载电阻RC有关,称为直流负载线。(4)求静态工作点Q,并确定UCEQ、ICQ的值。晶体管的ICQ和UCEQ既要满足IB=40μA的输出特性曲线,又要满足直流负载线,因而晶体管必然工作在它们的交点Q,该点就是静态工作点。由静态工作点Q便可在坐标上查得静态值ICQ和UCEQ。
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