27.1 A 2.8µW 80mVpp-linear-input-range 1.6GΩ-input impedance bio-signal chopper amplifier tolerant to common-mode interference up to 650mVpp

Closed-loop neuromodulation with simultaneous stimulation and sensing is desired to administer therapy in patients suffering from drug-resistant neurological ailments. However, stimulation generates large artifacts at the recording sites, which saturate traditional front-ends. The common-mode (CM) artifact can be ∼500mV, and the differential-mode (DM) artifact is 50 to 100mV. This work presents a neural recording chopper amplifier that can tolerate 80mVpp DM and 650mVpp CM artifacts in a signal band of 1Hz to 5kHz. To digitize a 2mVpp neural signal to 8b accompanied by an 80mVpp DM artifact requires a linearity of 80dB. Neural recording front-ends also need to function within a power budget of 3 to 5µW/ch, input-referred noise of 4 to 8µVrms, DC input impedance Zin>1GΩ and high-pass cutoff of 1Hz [1,2]. Prior work has addressed power and noise [2–6], but has low Zin and limited input signal range, making them incapable of performing true closed-loop operation.