A 89-dB DR 457-mu W 20-kHz bandwidth delta-sigma modulator with gain-boosting OTAs

Abstract

This paper presents a low-power, high-resolution delta-sigma modulator for use in portable devices. The modulator architecture uses a mixed-loop topology, having both feedback and feedforward paths. A new fully differential operational transconductance amplifier is designed that has a higher slew rate and a higher dc gain than conventional amplifiers. A 0.5-mm(2) modulator chip is implemented in a standard 0.25-mu m CMOS process and operates with a 1.5-V power supply. Measurement results demonstrate a 89-dB dynamic range in a 20-kHz bandwidth with only 457 mu W of power consumption.