An area-efficient low-noise bio-sensing amplifier with continuous-tunable gain

This paper presents a low-power area-efficient instrumentation amplifier (IA) for biopotential recording. The proposed IA adopts a resistor-controlled-oscillator (RCO) to change the mid-band gain of the readout circuit for different biomedical applications. The switched-capacitor load of the IA changes with RCO's output frequency, making the gain of IA continuous tunable. Measurement results show that the input referred noise of proposed IA is about 1.2µVRMS (BW=150Hz) and the NEF is 3.75. The range of tunable gain is from 22 to 35dB. And the measured CMRR and PSRR at 50Hz are larger than 70dB. The power consumption of the IA is 790nW at 1.2V supply. The active area of the IA is 0.035mm2.