节点电压方程怎么写
节点电压法;
U1(1/R3+1/R1+1/R2) - U2/R1 - U3/R2 = Us/R3;
U3(1/R4+1/R2) - U1/R2 = Is + 2*I2/R4;
U2 = -0.5*U = -0.5*(U1-U2);
I2 = (U1-U3)/R2;
解得 :U1=-U2=1,U3=3;