Design and performance of a noise shaping, pulse width modulated, digital to analogue converter

Describes the implementation of an audio DAC which is based on oversampled, noise shaped pulse width modulation. The basic principles of oversampled noise shaping (ONS) and pulse width modulation (PWM) are outlined, with particular reference to how ONS is used to relax the design specifications of the PWM circuit. The DAC has been tested by measuring its response to digitally generated tones from a commercial test disc via an 8x oversampling CD player. The results of these tests are shown to be in close agreement with previous theoretical and computer simulation results. Furthermore, ONS PWM is shown to be suitable for the direct conversion of digital audio data into analogue power using a fast MOSFET power switch, subject to switching efficiency considerations highlighted by Hiorns, et al. (ibid., p.4/4-4).<
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