A 15.5b-ENOB 335mVpp-Linear-Input-Range 4.7GΩ-Input-Impedance Direct-ADC Based Analog Front-End

Wearable electromyography (EMG), electroencephalography (EEG), and electrocardiography (ECG) systems offer a cost-effective means to access one’s heart, muscle, and brain activities through surfaceelectrode recordings on the human body. In order to capture various biopotential (ExG) signals down to $\mu$V level without distoition in the presence of DC electrodes offset, common-mode interference, and motion artifacts (Fig.1), analog front-end (AFE) with very low noise (<100nV/$\sqrt{\mathrm{Hz}}$) and large linear input range (>300m$\mathrm{V}_{\mathrm{p}\mathrm{p}}$) is essential. Moreover, to enable gel-free ExG recordings, the AFE must exhibit much higher input impedance (>100M$\Omega$@50Hz) than the electrodetissue impedance to prevent signal attenuation and maintain a high total common-mode rejection ratio (T-CMRR) in practice.