This thesis pertains to analog closed-loop Pulse Width Modulation (PWM) Class-D audio amplifiers with specific emphasis on nonlinearities, or equivalently fidelity. The specific nonlinearities investigated are the power supply noise-related nonlinearities, harmonicrelated nonlinearities and the intermodulation-related nonlinearities. Arising from the investigations herein, the mechanisms of these nonlinearities are modeled and thereafter, analytical expressions are derived to provide a means to determine the magnitude of these nonlinearities. At this juncture, it is recognized that analog PWM Class-D amplifiers are inferior to their linear counterparts in terms of the usual measure for power supply noise immunity, qualified by Power Supply Rejection Ratio (PSRR). Further, the present modeling thereof is imprecise and incomplete. In this thesis, the modeling of the mechanisms of power supply noise based on multi-dimensional Fourier series analysis is proposed and this modeling is shown to be precise. Further, it is shown herein, for the first time, that three other nonlinearities related to the power supply noise – harmonic PSRR, Power Supply-induced Intermodulation Distortion and Power Supply-induced Foldback Distortion – exist and they can be significant. The mechanisms for these nonlinearities are modeled and analytical expressions derived to provide a means to determine the magnitude of these nonlinearities.

Doctor of Philosophy