NeuroMonitor: a low‐power, wireless, wearable EEG device with DRL‐less AFE

Electroencephalography (EEG) is an effective tool to non‐invasively capture brain responses. Traditional EEG analogue front end (AFE) requires a driven right leg (DRL) circuit that restricts the number of channels of the device. The authors are proposing a new ‘DRL‐less’ AFE design, and have developed a wearable EEG device (NeuroMonitor), which is small, low‐power, wireless, and battery operated. The EEG device with two independent channels was fabricated on an 11.35 cm 2 PCB that contained a system‐on‐a‐chip microcontroller, a low‐noise instrument amplifier, a low‐power Bluetooth module, a microSD, a microUSB, and a LiPo battery. The DRL circuit was eliminated by utilising the high CMRR instrument amplifier with differential inputs, and followed by a modified high‐Q active Twin‐T notch filter (( f c Notch  = 60 Hz,  − 38 dB). The signal was conditioned with a band‐pass filter composed of a two‐stage 2nd‐order Chebyshev‐I Sallen‐Key low‐pass filter cascaded with a passive 2nd‐order low‐pass filter ( f c LP  = 125 Hz) and a 1st‐order passive high‐pass filter ( f c HP  = 0.5 Hz). Finally, the signal was amplified to achieve an overall gain of 55.84 dB, and digitised with a 16‐bit delta‐sigma ADC (256 sps). The prototype weighs 41.8 gm, and has been validated against a research‐grade EEG system (Neuroscan).