A low-voltage low-power sigma-delta modulator for bio-potential signals

This paper presents the design and implementation of a low-power, low-voltage sigma delta modulator (SDM) with a standard 0.18μm CMOS technology. A novel cascode current mirror operational trans-conductance amplifier (OTA) is utilized to enlarge the input common-mode range. The one-stage OTA structure is simple and low-power comparing with the traditional multi-stage folded cascode structure. The designed modulator achieved 68.6-dB signal-to-noise-and-distortion-ratio (SNDR) in 10-kHz bandwidth with an oversampling ratio of 64. The power consumption was 60μW with an 0.9-V power supply.