Low-power integrated circuits for wearable electrophysiology

This chapter presents an overview of the fundamentals and state of the art in non-invasive biopotential recording instrumentation with a focus on micro-power integrated circuit design for high-density and unobtrusive wearable applications. Fundamental limits in sampling, noise, and energy efficiency in the design of front-end biopotential amplifiers and acquisition circuits are reviewed, and practical circuits that approach these limits using metal-oxide semi-conductor transistors operating in the subthreshold and weak-inversion regime are presented. Analog-to-digital converters (ADCs) for low-power applications are reviewed with a focus on successive-approximation-register ADC and ΔΣ ADC, along with some other alternative ADC architectures. Basic low-power design techniques for digital circuits and architectures are also reviewed with points of references. Examples are given of practical ultra-low-power circuits for biomedical wearable applications.