An Adaptive Averaging Low Noise Front-End for Central and Peripheral Nerve Recording

An adaptive averaging low noise analog frontend (AFE) is presented for central and peripheral nerve recording applications. The proposed topology allows users to trade off, on the fly, between input referred noise and the number of channels via averaging. The new low noise amplifier (LNA) utilizes a complementary doubled input transconductance (g
_m
) topology to effectively increase the noise efficiency factor without chopping or use of a costly BiCMOS process. It addresses a disadvantage of the doubled-g
_m
technique by a high input impedance DC-coupled LNA and saves on-chip space for higher density by eliminating AC-coupling capacitors. The proposed technique is particularly suitable for ultra-low noise multichannel recording from the peripheral nervous system with a channel selection analog multiplexer, where the input signal is in tens of μV. A 32-ch proof-of-concept-prototype AFE was fabricated in a 5M2P 130-nm standard CMOS process, occupying 2.4 × 2.5 mm
²
together with its control block. The prototype LNA consumes 11 μW from a 1-V supply, providing 3.0-μVrms input referred noise with 61-MΩ input impedance, which are desirable for high SNR, to be further improved by the adaptive averaging technique.