两个电阻R1,R2,串联,R1接+3.3V,R2接-15V,中点电压怎么求?仿真是0.91,不知道怎么算出来的,仿真如下图已经做了实验,真是0.91V左右
节点电压法:
Uc*(1/R1+1/R2) =Ua/R1 +Ub/R2
Uc=(Ua*R2 + Ub*R1)/(R1+R2)
Uc=(3.3*20 - 15*3)/23 = 21/23 = 0.913(V)
支路电流法:
Uab = Ua - Ub = 3.3+15=18.3V;
R = R1+R2 = 23k;
I = Uab/R;
Uc = Ua - I*R1 = 0.913(mA)