Performance analysis of a DRL-less AFE for battery-powered wearable EEG

The driven-right-leg (DRL) circuit has been commonly used in the wall-powered EEG systems to reduce common-mode interference in the bio-potential amplifier. However, DRL circuit imposes limitations on the number of channels preventing modular development, and its effectiveness is diminished for a newer generation of battery-powered EEG systems. We present a performance investigation of DRL-less EEG circuit by designing a single-channel EEG with a novel Analog Front End (AFE) that contains a differential amplifier followed by a high-Q active notch filter. The prototyped wearable EEG system has been validated to record neural signals with and without the DRL circuit. The time domain and frequency domain signals show that the designed AFE is not impacted significantly (maximum 4 dB difference) by the DRL elimination and maintains similar signal quality. The customized EEG with and without DRL offers CMRR of 72.98 dB and 71.74 dB, respectively, at 60 Hz (power-line interference range in the USA), whereas CMRR of 72.64 dB and 71.01 dB, respectively, at 20 Hz (representative EEG signal range). DRL elimination allows us to envision a sensor-level modular EEG system for neural monitoring in non-clinical environments.