A modulator receiving an analog input signal and a switching signal for providing an amplitude modulated output signal. The modulator includes a differential input amplifier coupled to a multiplier wherein the analog input signal is commutated through a load resistor by the switching signals that are supplied to the multiplier. A gating circuit is coupled to the multiplier whereby the analog input signal is commutated to a feedback circuit coupled between the gating circuit and the second input of the differential input amplifier. The feedback circuit produces an output for adjusting the bias potential at the second input of the differential input amplifier to equalize the differential output currents therefrom when the analog input signal is set to a nominal zero level and the gating circuit is activated.