Low-Noise Two-Wired Buffer Electrodes for Bioelectric Amplifiers

• Published in: IEEE transactions on biomedical engineering Vol. 54; no. 7; pp. 1328 - 1332
• Main Authors: Degen, Thomas, Torrent, Simon, Jackel, Heinz
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.07.2007; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Active electrodes; Amplifiers, Electronic; Bioelectric phenomena; bioelectric recordings; Computer-Aided Design; dc-offset compensation; Electric potential; Electrodes; Equipment Design; Equipment Failure Analysis; Immune system; Impedance; instrumentation amplifier; Instruments; Interference; Low-noise amplifiers; Microelectrodes; Transistors, Electronic; two-wired electrodes; Voltage; Wires
• ISSN: 0018-9294; 1558-2531
• DOI: 10.1109/TBME.2006.889781

Active buffer electrodes are known to improve the immunity of bioelectric recordings against power line interferences. A survey of published work reveals that buffer electrodes are almost exclusively designed using operational amplifiers (opamps). In this paper, we discuss the advantage of utilizing a single transistor instead. This allows for a simple electrode, which is small and requires only two wires. In addition, a single transistor adds considerably less noise when compared to an opamp with the same power consumption. We then discuss output resistance and gain as well as their respective effect on the common mode rejection ratio (CMRR). Finally, we demonstrate the use of two-wired buffer electrodes for a bioelectric amplifier.