A 0.04 mm2/Channel Neural Amplifier with An Input-Referred Noise of 4.6 µVrms and Power Consumption of 3 µW

This paper presents the design of a small-sized low-noise low-power analog front-end (AFE) amplifier for implantable multi-channel neural recording applications. The proposed amplifier consists of two stages, a chopper-stabilized capacitively-coupled instrumentation amplifier (CS-CCIA) followed by a programmable-gain amplifier (PGA). The amplifier can be set in either of the two modes: AP mode (300 ~ 10 kHz for capturing action potentials) and wide-band mode (1.5 ~ 10 kHz for capturing both local field potentials and action potentials). Depending on the neural signals of interest, the amplifier’s high-pass cut-off frequency for AP and wide-band modes is set by large pseudo resistors and a dedicated DC servo loop, respectively. In contrast to most existing designs in which the low-pass cut-off frequency is set by a dedicated filter circuit after the amplifier stages, the proposed amplifier sets a gain- independent low-pass cut-off frequency within the PGA, minimizing the size of the overall analog front-end. The proposed AFE has been fabricated using a 180-nm CMOS process, occupying a small area of 0.04 mm
²
. It consumes 3 μW under a 1.2-V supply. The input-referred noise is measured 4 µVrms in the action potential band and 4.6 µVrms in the wide band.