An investigation on the parameters affecting total harmonic distortion in class D amplifiers

In this paper, we investigate two important and practical design parameters for the design of low-voltage low-power class D amplifiers that may affect the Total Harmonic Distortion (THD): the linearity of the carrier waveform and the impedance of the output stage. By means of a novel mathematical analysis method to model the carrier non-linearity, we show that this non-linearity should be mitigated to achieve low THD. Our mathematical analysis also provides an insight to the degree of non-linearity acceptable for a practical design. We show that the impedance of the output stage has little effect on THD. We verify our analysis by means of MATLAB and SPICE simulations.