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Practical switching transition times typically occupy less than one percent of the switching period in class D audio amplifiers. These transitions, however, are a very nonlinear function of current, which give rise to significant levels of distortion. This paper presents a method for determining the effect of nonlinear switching transition curves on harmonic distortion within half-bridge and full-bridge topologies, taking into account the interaction between the various dominant pulse-timing errors. An accurate analytical model, based on the well-established double Fourier series method of analysis, for determining the effect on harmonic distortion is introduced. The analytical model is accompanied by an equivalent simulation model using an existing strategy, and the results are verified experimentally.