A Sub-μVRms Chopper Front-End for ECoG Recording

This paper presents a low-noise, low-power fully differential chopper-modulated front-end circuit intended for ECoG signal recording. Among other features, it uses a subthreshold source-follower biquad in the forward path to reduce noise and avoid the implementation of a ripple rejection loop. The prototype was designed in 0.18μm CMOS technology with a 1V supply. Post-layout simulations were carried out showing a power consumption below 2μW and an integrated input-referred noise of 0.75μV rms , with a noise floor below 50 nV√Hz, over a bandwidth from 1 to 200Hz, for a noise efficiency factor of 2.7.