A 110dB-CMRR 100dB-PSRR multi-channel neural-recording amplifier system using differentially regulated rejection ratio enhancement in 0.18μm CMOS

Multi-channel neural-recording amplifier systems have evolved into the method of choice for analyzing neurophysiological behavior, and are leading to a deeper understanding of the human brain [1-4]. Such systems operate from a noisy supply and ground, especially when they are powered wirelessly. As shown in Fig. 29.7.1, the amplifiers ought to be low-noise, low-power, and resilient against environmental noise and interferences that are capacitively coupled from the power lines (220V/60Hz). Specifications-wise, these requirements translate into high CMRR, TCMRR, and PSRR. TCMRR (total CMRR) is a more realistic specification than CMRR as it includes the effect of the impedances of both electrodes (Z
e
) and the amplifier input (Z
Cin
) as well. In fact, the TCMRR should be >70dB for reliable detection of a 5μV
rms
neural signal [1].