Nerual signal recorder with tunable gain amplifier using low transconductance OTA

In this paper, multi-channel neural signal recorder with tunable gain filter is proposed. It is characterized by small-gm OTA for lowering cutoff frequency. The prototype of the proposed system is designed in TSMC 0.18 μm CMOS technology. Filter consists of high pass filter of delta-gm structure OTA with 201.06 pA/V transconductance and tunable gain Gm-C low pass filter. Single slope ADC is used to convert filter output into digital bits. The tunable gain range, bandwidth, CMRR and input referred noise of resulting filter are 20-68 dB, 20 Hz-10 kHz, 185.7 dB at 5 kHz and 319 nV/VHz, respectively. Single slope ADC has 40 kS/s sampling rate and 1.2 V input range. Total power consumption per channel is 59 μW.