A mixed-signal analogue front-end for brain-implantable neural interfaces using a digital fixed-point IIR filter and bulk offset cancellation

TL;DR

This paper introduces a mixed-signal analogue front-end for neural interfaces that combines low-noise amplification, digital filtering, and offset cancellation to effectively record brain signals.

Contribution

It presents a novel mixed-signal AFE integrating a fixed-point IIR filter and bulk offset cancellation for neural recording applications.

Findings

Achieves up to 41.42dB gain and 3.59uVrms noise level.

Consumes 2.178uA per channel and occupies 0.198mm2.

Supports neural signals from 0.1Hz to 10kHz.

Abstract

Advances in miniaturised implantable neural electronics have paved the way for therapeutic brain-computer interfaces with clinical potential for movement disorders, epilepsy, and broader neurological applications. This paper presents a mixed-signal analogue front end (AFE) designed to record both extracellular action potentials (EAPs) and local field potentials (LFPs). The feedforward path integrates a low-noise amplifier (LNA) and a successive-approximation-register (SAR) analogue-to-digital converter (ADC), while the feedback path employs a fixed-point infinite-impulse-response (IIR) Chebyshev Type II low-pass filter to suppress sub-mHz components via bulk-voltage control of the LNA input differential pair using two R-2R pseudo-resistor digital-to-analogue converters (DACs). The proposed AFE achieves up to 41.42dB gain, consumes 2.178uA per channel, occupies 0.198mm2 per channel, and supports neural signal monitoring from 0.1Hz to 10kHz with 3.59uVrms input-referred integrated noise.