Low noise amplifier for recording ENG signals in implantable systems

In this paper, a low noise amplifier used to sense ENG signals with amplitudes greater than 1 /spl mu/V/sub p/ has been designed and fabricated in 0.7 /spl mu/m CMOS technology. The electrical characterization and results in acute experiments with rats are presented. The main characteristics are: low noise (5 nV/sub rms///spl radic/Hz), high CMRR (>90 dB), programmable gain (77 dB-103 dB), bandpass from 100 Hz to 5 kHz and tolerance to the input offset greater than /spl plusmn/50 mV. In order to implement the low cut-off frequency of the band pass filter, an active resistor of 80 M/spl Omega/ value has been designed with programmable tuning.