Class-D amplifiers are two to four times more efficient than Class-AB amplifiers and provide a solution for applications where lower supply current, lower heat dissipation or longer battery life are necessary. However, traditional Class-D amplifiers introduce other problems: increased solution size and cost. These Class-D amplifiers require an output filter to operate. A new modulation scheme has been developed to eliminate the need for an output filter. This paper discusses the advantages of Class D over Class AB and focuses on the details of the new modulation scheme and why it enables filterless operation. This paper also discusses the effect that eliminating the output filter has on supply current, efficiency, sound quality, and electromagnetic interference (EMI).
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