An 18µW 79dB-DR 20KHz-BW MASH ΔΣ modulator utilizing self-biased amplifiers for biomedical applications

This paper presents a micro power, area-efficient 4^th-order MASH delta-sigma modulator based on a novel self-biased amplifiers for neural sensing applications. A high-gain self-biased CMOS amplifier is proposed to achieve low power operation. Floating correlated double sampling technique is devised to enhance the amplifer´s gain-linearity and hence the modulator´s SFDR and SNDR performance. Fabricated in a 0.13 μm CMOS process, the prototype achieves 71 dB peak SNDR and 79 dB peak DR over 20 KHz neural signal bandwidth, while occupying only 0.06 mm² silicon area. By optimizing the power budgets for different amplifiers, the MASH modulator consumes only 18 μW from 1.5 V supply. The proposed circuit techniques can be applied to other operational transconductance amplifier-based circuits for low power, high speed, and area-efficient design.