A highly-accurate low-power CMOS potentiostat for implantable biosensors

Current-mirror-based potentiostats suffer from systematic and random errors causing offset, gain and linearity error in reading out the sensor data. In this work, a new potentiostat topology is proposed to eliminate the systematic error via an error-cancellation loop. The loop takes advantage of an error-tracking amplifier connected to a transimpedance amplifier with adjustable input common-mode voltage. Due to the enhanced loop gain, the potentiostat is able to accurately copy the sensor current which will then be converted into the proportional voltage. Additionally, a theoretical discussion of the proposed topology is given and a thorough study on the effect of random error sources is carried out. The potentiostat is designed and simulated in a 150nm CMOS process. The results verify a highly-linear highly-accurate performance in a low-noise condition, while consuming only 32 μW.