结合电路讲解一下基于场效应管的恒流电路是怎么工作的工作原理?

2025年03月15日 20:06
有2个网友回答
网友(1):

npn三极管q2是负载电流检测用,vmos场效应管q1是恒流调整用,当负载的电流达到1.35a至1.58a
时,电流取样电阻r2二端的电压差达到三极管q2
e、b结的正向导通电压0.6至0.7v,于是该管从放大区进入饱和区,饱和导通时其c、e极之间的导通内阻减小(ce极饱和电压是0.1v至0.2v),三极管q2的
c、e结将场效应管q1的栅极g及源极s通过电阻r2连接,由于电阻r2阻值0.443欧姆很小,场效应管q1的栅极g及源极s近似短路,vcc电源通过电阻r1送往场效应管q1栅极g的正向导通偏置电压通过三极管q2
c、e结和电流取样电阻r2形成分压回路,使场效应管q1栅极g对源极s的正偏压减小,使该管d、s导通程度降低,限制了负载电流增加,起到恒定电流作用,根据电流取样电阻r2阻值是0.443欧姆,计算出恒定电流范围维持在1.35a至1.58a
之间。

网友(2):

要想整明白这个电路,你要先明白场效应管工作原理,管子的导通或导通程度是由管子的GS两端的电压决定的。管子下面不是有个反馈电阻吗,当管子有电流流过的时候,这个电阻上产生电压降,比如电阻是一欧的,流过一安电流,电阻上的压降就是一伏,电阻上压降升高一伏,就相当于管子的GS电压降低了一伏,管子的导通电阻会增大,阻止电流的进一步增大,管子在这个电路中就相当于一个可变电阻。

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