A 1.7x4.1x2 Mm(3) Fully Integrated Ph Sensor For Implantable Applications Using Differential Sensing And Drift-Compensation

This paper presents a 1.7x4.1x2 mm(3) pH sensor that is a fully integrated, stand-alone and implantable system. Instead of a bulky cm size Ag/AgCl electrode, we use a mm-size integrated platinum electrode, and differential sensing using ISFET and REFET pair to compensate for unstable fluid potential. We also propose a drift compensation technique in which the leakage from the source and drain through the gate oxide is canceled, reducing drift >100X.