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

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 × 2 mm
²
180-nm CMOS chip, and each channel consumes 4 μW, achieves an input referred noise of 160 nV/√ Hz, and an ADC effective number of bits of 8.5 bits.