A low-noise chopper amplifier for bio-signal recording is described. Potential applications include many-electrode implantable ECG acquisition systems along with EEG, EMG and ECoG bio-signals. Designed in 0.13µm CMOS, the two-stage amplifier uses a folded cascode topology with a low-impedance node chopping technique combining both voltage and current-mode chopping for an optimal noise and bias current tradeoff while significantly reducing ripple from the 40 KHz chopper modulation signal. Experimental results show an amplifier with digitally programmable gain from 40 – 83 dB, bandwidth from 340 – 7.5 KHz and high pass cutoff of 170 mHz, while dissipating only 1.1 µW from a 1.2 V supply. The inputreferred noise is 2.1 µVrms integrated over a 100 mHz – 100 KHz bandwidth with a noise efficiency factor of 3.28.
['Christopher John Mandic', 'Daibashish Gangopadhyay', 'David J. Allstot']
A 1.1µW 2.1µVRMS input noise chopper-stabilized amplifier for bio-medical applications