A 1.8V CMOS fourth-order Gm-C bandpass sigma-delta modulator dedicated to front-end ultrasonic receivers

A 4th-order bandpass /spl Sigma//spl Delta/ modulator for ultrasound applications is presented. By cascading 2 identical 2nd-order Gm-C filters, the 4th-order modulator is designed with high power efficiency, stability and programmability. The modulator dynamic range is 78dB over a 200kHz bandwidth around IF frequency of 3 MHz. The modulator has been implemented in a standard 0.18 /spl mu/m CMOS technology and consumes 2.5 mW from 1.8V power supply.