Patent ID: 8093951

Claim:
An audio amplifier circuit for providing an output signal to an audio transducer in response to an audio input signal, said audio amplifier circuit comprising: a pulse-width modulator for generating a pulse-width modulated version of the output signal from a representation of the audio input signal, the pulse-width modulator having an output stage with multiple power supply inputs having a voltage determinative of the amplitude of pulses generated by the pulse-width modulator output stage, and wherein the pulse-width modulator is responsive to one or more selection signals to select a selected one of the multiple power supply inputs to set the amplitude of the pulses; and a control circuit for providing the one or more selection signals, wherein the control circuit generates the one or more selection signals according to an indication of a desired amplitude of the output signal, wherein the pulse width modulator comprises multiple switching circuits for generating the pulse-width modulated version of the output signal, wherein the control circuit is coupled to control inputs of each of the switching circuits for controlling switching of the switching circuits, wherein the switching circuits are coupled to corresponding ones of the multiple power supply inputs, wherein the control circuit disables switching of all except a selected one of the multiple switching circuits to select a corresponding one of the multiple amplitude levels for the pulses, and wherein a rate of the pulses generated by the pulse-width modulator is selected in conformity with the indication of the desired amplitude of the output signal.