A DC-coupled 1.2 μW 0.012 mm2 per channel neural amplifiers array with 75 dB system common mode rejection ratio and 300 mV common mode interference

System common mode rejection ratio (SCMRR) and common mode interference (CMI) range are two critical design specifications for multiple-channel neural recording front-end circuit in a freely moving animal experiment environment. This letter presents a neural amplifiers array consisting of 15 DC-coupled inverter-based recording channels, a reference channel and a shared voltage averaging circuit (VAC) with floating rail Common Mode Feedback (CMFB) to achieve high SCMRR and large CMI range. Meanwhile, power consumption and area are optimized through using simple inverter architecture and removal of the conventional on-chip AC-coupled capacitors. The proposed neural amplifier circuit is implemented in SMIC standard 0.18 mu m CMOS process, achieving a typical 75 dB SCMRR (DC-80 Hz), 300 mV CMI range, 1.2 mu W power consumption and 0.012 mm(2) area per channel. The circuit is validated both by bench-top test and in-vivo animal experiment.