| 摘要 |
A novel circuit that generates direct audio from a power supply (+V) that uses no power amplifier and that can provide full isolation to any impedance load. It has no power amplifier output stage and has a zero signal-to-noise ratio when there is no signal input because the circuit is designed with MOSFETS that do not conduct unless there is a signal input. The circuit includes an input rectifier (18) for rectifying an input audio signal (12), a pulse width modulator (22) for producing a signal modulated by the rectified audio signal, a power amplification stage (24) for amplifying the pulse width modulated signal, a positive/negative rectifier pair (50, 52, 56, 58) for positively and negatively rectifying the amplified pulse width modulated signal, a demodulator (62) for demodulating the positively and negatively rectified signal in order to generate a power amplified audio signal and a switching network (54, 60) for directing the positively rectified signal to the demodulator in response to the signal polarity detector (20) sensing a first polarity of the input audio signal, and for directing the negatively rectified signal to the demodulator in response to the signal polarity detector sensing a second polarity of the input audio signal. A low power embodiment uses a single power supply to bias push-pull transistors, a medium power embodiment uses positive and negative rails individually to bias the push-pull transistors, and a high power embodiment uses the additive sum of the positive and negative rails to bias the push-pull transistors.
|
