A low-voltage MOSFET-only /spl Sigma//spl Delta/ modulator for speech band applications using depletion-mode MOS-capacitors in combined series and parallel compensation

An area-efficient high-linearity MOSFET-only /spl Sigma//spl Delta/ modulator using depletion-mode MOS-capacitors in combined series and parallel compensation technique is presented. The new approach joins the advantages of the series and parallel compensation of depletion-mode MOS-capacitors, achieving an optimum of linearity and area efficiency. The 2/sup nd/-order fully-differential MOSFET-Only /spl Sigma//spl Delta/ modulator was implemented in a standard 0.25 /spl mu/m n-well digital CMOS process without extra layers for capacitors. The circuit operates at 1.8 V supply voltage, consumes 1 mW and achieves a SNR of 77 dB and a SNDR of 71 dB at a signal bandwidth of 8 kHz. The occupied core area is 0.06 mm/sup 2/.