CMOS Switched-Capacitor Circuits: Applications in Biomedical and RF Systems

Monday, November 02, 2015
11:00 AM to 12:00 PM
UTA 7.532
Free and open to the public

Switched-capacitor circuits have been used in high-volume data converters and signal processing ICs for nearly four decades, and are ubiquitous in modern RF transceiver circuits and emerging as a dominant design approach in CMOS bio-medical circuits and systems. 

Body-area-networks (BAN) that integrate multiple sensor nodes in portable and wearable bio-medical systems are revolutionizing healthcare. A typical BAN comprises several bio-signal and motion sensors and uses ultra-low-power short-haul radios in conjunction with nearby smart-phones or handheld devices (with GPS capabilities) to communicate via the internet with a doctor or other healthcare professional. Higher energy efficiency is critical to the development of feature-rich, wearable and reliable personal health monitoring systems. 

The amount of data transmitted to the smart-phone increases as more sensors are added to the BAN. Because the energy consumed for RF transmission is proportional to the data rate, it is advantageous to compress the bio-signal at the sensor prior to digitization and transmission. This energy-efficient paradigm is possible using compressed sensing—a sampling theory wherein a compressible signal can be acquired using only a few incoherent measurements. For ECG signals, for example, large compression factors are achievable which means similar reductions in energy consumption. 

The RF power amplifier dissipates a large fraction of the total power of a transceiver because of its low efficiency. Despite more than two decades of extensive research, the challenge of on-chip RF Pas with high efficiency in digital-friendly CMOS technologies has not been met. Switching PA topologies with relatively high efficiency have gained momentum, and relatively high output power is being delivered using power combining techniques. Supply regulation techniques have enabled higher efficiency when amplifying non-constant envelope modulated signals. The switched-capacitor RF power amplifier technique which meets many of the remaining challenges is described. 

This talk also overviews other techniques for future bio-signal acquisition systems including switched-capacitor ring amplifiers.

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David Allstot

David J. Allstot

University of California, Berkeley

David J. Allstot received the B.S., M.S., and Ph.D. degrees from the Univ. of Portland, Oregon State Univ., and the Univ. of California, Berkeley. 

He has held several industrial and academic positions. He was the Boeing-Egtvedt Chair Professor of Engineering at the Univ. of Washington from 1999 to 2012 and Chair of the Dept. of Electrical Engineering from 2004 to 2007. In 2012 he was a Visiting Professor of Electrical Engineering at Stanford University and since 2013 he is the MacKay Professor in Residence in the EECS Dept. at UC Berkeley. 

Dr. Allstot has advised approximately 65 M.S. and 40 Ph.D. graduates, published more than 300 papers, and received several awards for outstanding teaching and research including the 1980 IEEE W.R.G. Baker Award, 1995 and 2010 IEEE Circuits and Systems Society (CASS) Darlington Award, 1998 IEEE International Solid-State Circuits Conference (ISSCC) Beatrice Winner Award, 2004 IEEE CASS Charles A. Desoer Technical Achievement Award, 2005 Semiconductor Research Corp. Aristotle Award, 2008 Semiconductor Industries Assoc. University Research Award, 2011 IEEE CASS Mac Van Valkenburg Award, and 2015 IEEE Trans. on Biomedical Circuits and Systems Best Paper Award. He has been active in service to the IEEE Circuits and Systems and Solid-State Circuits Societies throughout his career.