This paper describes an analog front-end （AFE） intended for portable audio application, which operates at 1 V and consumes only 410 μW. The AFE consists of a 30 dB-gain programmable gain amplifier （PGA） and a 2nd-order 3-bit sigma-delta modulator. The PGA with single input and on-chip common-mode bias voltage shows good noise-reduction performance. The modulator makes use of data weighted averaging to reduce the linearity requirements of the digital-to-analog converter in the feedback loop. The AFE is implemented in the SMIC 0.13μm 1PSM CMOS process. The measurement results show that in a 1 V power supply, at 200 mVp-p, between 100 Hz and 20 kHz, the maximal signal-to-noise ratio is 70 dB, and the total power is 410 μW.
