Linearized three-state switching amplifier

Abstract

A pulse width modulated switching amplifier is provided for amplifying an analog signal. Means is provided for producing positive and negative signals representative of positive and negative excursions of the analog signal, respectively. The positive and negative signals are applied to level shifters which produce positive and negative replica signals having the same waveshapes as the positive and negative signals, respectively, but which vary about a predetermined reference level. The level shifted replica signals are then applied to first and second comparators, respectively, which continuously sum the instantaneous magnitude thereof with the instantaneous magnitude of a triangular modulation signal also varying about the reference level. Each comparator produces a logical ONE output signal when the sum is positive and a logical ZERO output signal when the sum is negative. A switching circuit receives the logical signals from the comparators and produces an output pulse of one polarity when both comparators are producing logical ONE signals, an output pulse of the opposite polarity when both comparators are producing logical ZERO signals, and no output when the comparators are producing unlike logical signals. The output pulses are applied to a demodulator which produces an amplified replica of the analog signal.