3. A CUSTOM INTEGRATED HIGH INPUT IMPEDANCE BIOPOTENTIAL AMPLIFIER FOR NON-CONTACT AND MOBILE HEALTH (ECG/EEG) MONITORING

Department: Bioengineering
Faculty Advisor(s): Gert Cauwenberghs
Award(s): Department Best Poster

Primary Student
Name: Yu Mike Chi
Email: m1chi@ucsd.edu
Phone: 469-951-2227
Grad Year: 2011

Abstract
Ubiquitous physiological monitoring will be a key driving force in the upcoming wireless health revolution. Cardiac and brain signals in the form of ECG and EEG are two critical health indicators that directly benefit from long-term monitoring. Despite advancements in wireless technology and electronics miniaturization, however, the use of wireless home ECG/EEG monitoring is still limited by the inconvenience and discomfort of wet, contact electrodes.

Non-contact electrodes, which do not require direct electrical skin contact, have been long studied as a patient-friendly alternative. However, the poor coupling (high impedance) of the non-contact interface between patient and instrumentation have made producing practical sensors difficult. Implementations using currently available, discrete, off-the-shelf, components commonly require expensive parts in conjunction with manual calibration to achieve acceptable performance. Achieving the full noise and frequency response specifications necessary for a diagnostic grade signal (eg. AAMI ECG standards) have only been possible with extensive lab bench tuning of each electrode produced.

With these limitations in mind, we have designed a custom integrated circuit specifically to surpass the limitations encountered in discrete designs. Our custom non-contact electrode achieves an ultra-high input impedance (50TOhms | 60fF), a factor of 50 improvement compared to the best commercial amplifiers, completely without the need for manual adjustment. In addition, the sensor achieves a very low noise floor (.05fA/Hz^0.5), factor of 2.3 better than the best commercially available component, to ensure that integrated sensor adds minimal noise, even at very high source impedances encountered in non-contact physiological sensing. The amplifier includes on-chip input biasing circuits which maintain input stability while preserving the full frequency response necessary to achieve clinical ECG standards, even in the complete absence of a galvanic path to the patient. Finally, the sensor consumes only 5 microwatts per channel, making it amenable to long-term, mobile, low-power vital signs monitoring platforms.

Related Links:

  1. http://www.jacobsschool.ucsd.edu/news/news_releases/release.sfe?id=955
  2. http://www.isn.ucsd.edu/pubs/wh2010.pdf

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