Filterless multi-level delta-sigma class-D amplifier for portable applications

Abstract

A 2W filterless class-D amplifier using multi-level delta-sigma modulation is presented. LC filters consume large PCB space and add significant system cost, so filterless class-D solutions are preferred for portable applications. In this design, a multi-level, delta-sigma modulator is implemented to achieve high efficiency and high performance without the use of a filter. Although the modulator internally generates an 8MHz clock, the average switching frequency of output signal is dynamically reduced to 300kHz to minimize switching loss. Analog feedback from the output stages along with common-mode control yields 0.003% total harmonic distortion, and 103dB dynamic range.