A low noise CMOS amplifier for ENG signals

The development of an integrated amplifier, intended to record electrical signals from extracellular peripheral nerves, using cuff electrodes, is presented. In order to minimize the flicker noise generated by the CMOS circuitry, a chopper full differential amplifier is implemented. The amplifier has a gain of 74 dB, a bandwidth of 3 kHz and a power dissipation of 1.3 mWatts, with 5 V power supply. Equivalent input-referred noise level of 6.6 nV/(Hz)^0.5 has been achieved, obtaining a noise efficiency factor of 5.3, which is clearly competitive, compared with other developed recording amplifiers reported in the literature. The amplifier has been fabricated with a fully CMOS 0.7 μm technology (one poly, two metals, self aligned twin-well CMOS process) and the active area is 2.7 mm². In vivo nerve recordings are provided to demonstrate the feasibility of the amplifier.