Low-Power Integrated Circuit Design for Wearable Biopotential Sensing

This chapter presents an overview of the fundamentals and state-of-the-art in non-invasive biopotential recording instrumentation with a focus on micropower-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-semiconductor (MOS) transistors operating in the subthreshold and weak-inversion regime are presented. The electrode-body interface is shown to be a performance limiting factor in practical non-invasive wearable systems, and examples are given of practical interface circuits and electrode systems for dry-contact and non-contact biopotential sensing obviating the need for gel or electrolytic ohmic contact to the body.