A Current-Mode Capacitively-Coupled Chopper Instrumentation Amplifier for Biopotential Recording With Resistive or Capacitive Electrodes

Abstract

This brief presents a high-density, low-noise analog front-end (AFE) for capacitively coupled neural recording applications. Conventional capacitively coupled AFEs, when chopper-stabilized, require large coupling capacitors or servo loops to minimize $ {1/f^{2}}$ input-referred noise and chopper-induced offsets, limiting channel density. In this brief, a current-mode capacitively coupled chopper instrumentation amplifier with embedded delta-sigma analog-to-digital converter (ADC) is presented that enables an area-efficient low-noise design via chopper-stabilized current-mode amplification. In this design, 60 channels are implemented in a $ {2 \times 2}$ mm2 180-nm CMOS chip, and each channel consumes $4~ {\mu }\text{W}$ , achieves an input referred noise of 160 nV/ $\sqrt {\text{Hz}}$ , and an ADC effective number of bits of 8.5 bits.