由拉普拉斯变换，对R:Z(s)=R I1(s)=U(s)/R对L:I2(s)=U(s)/sL+i(0-)/s Z(s)=sL对C:Z(s)=1/sC I3(s)=sCU(s)-Cu(0-)令初始条件为零，I1(s)+I2(s)+I3(s)=I(s)U(s)/R+U(s)/sL+sCU(s)=I(s)H(s)=U(s)/I(s)=sLR/(sL+R+s²RLC)
