| 摘要 |
A novel circuit that generates direct audio from a power supply 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 for rectifying an input audio signal, a pulse width modulator for producing a signal modulated by the rectified audio signal, a power amplification stage for amplifying the pulse width modulated signal, a positive/negative rectifier pair for positively and negatively rectifying the amplified pulse width modulated signal, a demodulator for demodulating the positively and negatively rectified signal in order to generate a power amplified audio signal, and a switching network for directing the positively rectified signal to the demodulator in response to the signal polarity detector 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.
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