The inverting summing amplifier using op amp outputs a voltage equal to the sum of the voltages it has in its inputs. The following explanation is based on an adder of three inputs, but applies to an adder of any number of inputs
Full wave rectifier using center tapped transformer
This full wave rectifier requires a center tapped transformer. This additional end on the secondary winding of the transformer divides the voltage in this winding into two equal voltages. This additional end is grounded.
The transformer transformation ratio or transformer turns ratio (K) is the quotient value obtained by dividing the number of turns of the primary winding (N1) and the number of turns of the secondary winding (N2). Then K = N1/N2
The current through the resistor and the capacitor is the same. The voltage VS is equal to the phasor addition of the voltage drop across the resistor (Vr) and the voltage drop across the capacitor (Vc).