Low Distortion Analog Front-endfor Digital Electret Microphone

초록

This paper presents a low distortion analog front-end(AFE) circuit to process electret microphone output signal. A source follower is employed for the input buffer to interface electret microphone directly to the IC with level shifting. A single-ended to differential converter with output common-mode control is presented to compensate the common-mode variation resulted from gate to source voltage variation inthe source follower. A replica stage is adopted to control the output bias voltage of the single-ended to differential converter. The prototype AFE circuit fabricated in a 0.35 mu m CMOS technology achieves 68.2dB peak SNDR and 79.9dB SFDR over an audio signal bandwidth of20kHz with 2.5V supply while consuming 1.05mW.

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