An ultra low-power low-noise neural recording analog front-end IC for implantable devices

In this paper, a low-power, low-noise analog front-end integrated circuit (AFE IC) for neural signal recording is designed using 0.18-μm CMOS process. The proposed circuit consists of a low noise neural amplifier and a programmable gain amplifier with additional gain and bandwidth control to process signals in the 1 Hz to several kHz frequency band. The capacitive-feedback neural amplifier is designed using a complementary cascode input operational transconductance amplifier (OTA) for improved noise characteristics. The programmable gain amplifier, also based on capacitive-feedback architecture with a current mirror OTA, allows control of high-pass cutoff frequencies from sub-1 Hz to 220 Hz and low-pass cutoff frequencies from 530 Hz to 8.9 kHz. In addition, capacitive feedback with programmable cross-coupled input capacitors allows gain control from 6 dB to 24 dB without distortion. An integrated input noise of 4.74 μV_rms and noise efficiency factor of 2.91 are measured for the overall AFE IC at maximum gain setting. The IC consumes 2.28 μW of power from a 1-V supply and occupies 0.16 mm² of die area.