High efficiency class-I audio power amplifier using a single adaptive supply

Peng Zhenfei; Yang Shanshan; Feng Yong; Liu Yang; Hong Zhiliang

doi:10.1088/1674-4926/33/9/095002

Abstract: A high efficiency class-I linear audio power amplifier (PA) with an adaptive supply is presented. Its efficiency is improved by a dynamic supply to reduce the power transistors' voltage drop. A gain compression technique is adopted to make the amplifier accommodate a single positive supply. Circuit complicity and chip area are reduced because no charge pump is necessary for the negative supply. A common shared mode voltage and a symmetric layout pattern are used to minimize the non-linearity. A peak efficiency of 80% is reached at peak output power. The measured THD+N before and after the supply switching point are 0.01% and 0.05%, respectively. The maximum output power is 410 mW for an 8 Ω speaker load. Unlike switching amplifiers, the class-I amplifier operates as a linear amplifier and hence has a low EMI. The advantage of a high efficiency and low EMI makes the class-I amplifier suitable for portable and RF sensitive applications.

Key words: class-I, power amplifier, gain compression, adaptive supply, power efficiency

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Peng Z F, Yang S S, Feng Y, Liu Y, Hong Z L. High efficiency class-I audio power amplifier using a single adaptive supply[J]. J. Semicond., 2012, 33(9): 095002. doi: 10.1088/1674-4926/33/9/095002.

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