METHOD AND APPARATUS FOR FILTER-LESS CLASS D AUDIO AMPLIFIER EMI REDUCTION

摘要

An audio system includes a speaker and a class D amplifier with a class-D PWM (pulse width modulation) modulator configured for generating first and second PWM signals, each with three differential output levels. The class-D amplifier also has a differential output driver configured for driving a first and a second output signals onto a first and a second output terminals in response to the first and the second PWM signals, wherein each of the first and the second output signals has three differential output levels. An inverse common-mode signal generator is coupled to first and second output signals for providing an inverse common-mode signal. The audio system also includes one or more output terminals for providing the inverse common mode signal, and further includes a wire or a trace on a PCB (printed circuit board) inverse common mode signal.