Design of Transformerless Modulator-Demodulator

A transformerless modulator-demodulator that operates over a wide range of frequencies is described. The circuit is designed to exhibit symmetrical full wave rectification, to eliminate offset voltages at the output, and to lack the necessity of being fed from a voltage source. The equations to achieve these features are developed. To satisfy all these equations certain relations between various components must be observed. The solutions of these, obtained by a computer, are given for typical gains.