应用叠加定理,
Ui1单独作用时 Ui2 Ui3置短路,Ui1=Uo' x (R2并R3)/[Rf+(R2并R3)]
Ui1=Uo' x R2R3/(R2+R3)/[Rf + R2R3/(R2+R3)],Uo'=Ui1(RfR2+RfR3+R2R3)/(R2R3),
Ui2单独作用时 Ui1 Ui3置短路,Uo"=-Ui2 x Rf/R2,
Ui3单独作用时 Ui2 Ui1置短路,Uo'"=-Ui3 x Rf/R3,
Uo=Uo'+Uo"+Uo'"=Ui1+ Rf/R2(Ui1-Ui2) + Rf/R3(Ui1-Ui3)。