A 1.3μW 0.7μVRMS chopper current-reuse instrumentation amplifier for EEG applications

This paper presents a low noise chopper-stabilized instrumentation amplifier (IA) for EEG recording. The current-reuse technology is adopted to reduce noise of the IA and the regulated cascode circuit is used to boost the open-loop gain of the amplifier. A ripple reduction loop (RRL) based on a novel output-resistance-tuning technology is proposed to reduce the intrinsic offset of the IA and reduce the output ripple of the chopper amplifier. Simulation results show the high-pass cutoff frequency of 0.15Hz, the input referred noise of 0.7μV_RMS (BW=100Hz) and a NEF of 2.83. The attenuation to the chopping ripple is about 35dB with the novel output-resistance-tuning based RRL. The proposed IA achieves an average CMRR of 110dB, average PSRR of 105dB and average input-impedance of 1.5GΩ from Monte Carlo analysis. The overall IA consumes only 1.1μA current at a 1.2V supply.