Patent attributes
A class D audio amplifier provides both an audio output signal and a DC bias voltage to an electrostatic transducer (9). In the amplifier, a modulated sequence of pulses is generated by an input module (1) in response to an input audio signal. The sequence of pulses is amplified by an output module (3) using high speed switching output transistors (4, 5). An output signal is generated by applying a low pass filter (8) to the amplified pulses, and the output signal is provided to the transducer to produce audible output. The amplified sequence of pulses is also used to drive a voltage multiplier module (10) to provide bias voltage for the electrostatic transducer (9). In other embodiments, the bias voltage is provided by a bias voltage module which reverses the bias voltage at intervals, and a phase reverser (13) reverses the phase of the signals fed to the output module (3) simultaneously with reversal of the bias voltage.