Summing amplifier
= Summing amplifier
{title2=$V_o=-R_f\sum_jV_j/R_j$}
An inverting <operational amplifier> can combine currents from several input <resistors> at one <virtual ground>. <Kirchhoff's current law> and negligible amplifier input current give the displayed weighted sum. Replacing the feedback resistance by a <capacitor> gives a weighted <op amp integrator>. The formulas assume stable <negative feedback> and operation within the amplifier's linear output range.