| 摘要 |
<p>A practical power amplifier for directly producing analogue power from a digital input includes an oversampling filter (14) for increasing the pulse repetition rate and a noise shaping filter (18) for reducing the word length. Before the digital samples are fed to a pulse width modulator (20) their value is adjusted so that the output pulses produced by the modulator (20) approximate to those which would have been produced had a continuously varying representation of the digital samples been sampled by a periodic comparison waveform and then fed to the modulator. The detector (16) thereby enables the modulator to have the low distortion characteristics usual of naturally sampled analogue modulation, whilst the circuit accepts the regularly occurring digital samples from conventional digital devices.</p> |
