A High Input Impedance Fully-Differential Chopper Amplifier for Closed-Loop Neural Recording

This paper presents a chopper capacitively-coupled instrumentation amplifier (CCIA) with low power and low area consumption and high input impedance for closed-loop neural recording in the presence of in-band stimulation artifacts. A novel high linear pseudo resistor is used in DC servo loop (DSL) making the small high-pass cut-off frequency with small capacitor, and hence, reduced area occupation. With reducing the high-pass cut-off frequency, the positive feedback loop can also operate at low frequency. The proposed work has been simulated with Cadence using a 180 nm CMOS process. This chopper amplifier can tolerate 20 mV_p differential input and 520 mV_p common-mode artifacts while recording the small neural signal.