A Fully Integrated Chopper IA for Implantable Multichannel EEG Recording Without Impedance Boosting Circuits

A fully integrated chopper instrumentation amplifier for implantable multichannel EEG recording is proposed in this paper. It achieves high input impedance of 300 MΩ required by EEG signal sensing through a close-loop chopper structure based on differential instrument amplifier, without using extra boosting circuits. It also exhibits 1.06 μVrms of input-reference noise with an integrated bandwidth of 1 Hz to 100 Hz and has a digitally-controlled gain between 40 dB and 54 dB, CMRR of 105 dB at 50 Hz. AC-coupling is realized by using DC cancellation circuits, leading to a pass-band from 0.5 Hz to 5 kHz. The circuit was implemented in a standard 0.18 μm CMOS process and it consumes 0.66 μA with 1.2 V power supply. The chopper front-end demonstrates an excellent noise efficiency factor of 2.31 with 1 Hz to 5 kHz bandwidth.