Preamplifier Design for Active Electrodes in Single-Channel EEG Applications
Abstract: The implementation of portable electroencephalography (EEG) systems has been known to be complex. During ambulation, the integrity of recorded EEG signals is often impaired by motion artifacts and the time and effort required to set up the system is excessive. The use of single-channel EEG systems with dry, active electrodes (AEs) for signal acquisition is a topic of current interest. AEs are electrodes which have integrated bioamplifier circuitry and are known to be less susceptible to motion artifacts and environmental interference. In this report, the design of an AE preamplifier for the purpose of improving single-channel EEG recordings is presented. Initially, a thorough literature review was performed, exploring the available knowledge and state-of-the-art technology. Thereafter, the design specifications were set and the appropriate topology and circuit design techniques were selected to maximize the amplifier’s performance. Ultimately, three different preamplifier topologies were designed and their performance compared with one another as well as with established medical device standards and state-of-the-art AEs. The results of one preamplifier showed comparable performance with state-of-the-art AEs. Therefore, this topology was selected for a deep analysis and physical layout design. The layout of the selected preamplifier was designed and its parasitics extracted. The post layout performance of the design proved to be comparable to the schematic level performance, with a CMRR of 153dB, IRNV of 0.89µVRMS and an electrode offset tolerance of 450mV. The preamplifier design presented in this report has proven to be comparable with state-of-the-art AE preamplifiers and demonstrates potential for the advancement of AE performance in single-channel EEG systems.
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