A 0.72 nW, 1 Sample/s Fully Integrated pH Sensor with 65.8 LSB/pH Sensitivity

Abstract

This paper presents a 0.85 mm2 fully integrated pH sensor IC utilizing an ion sensitive field effect transistor (ISFET) and reference field effect transistor (REFET) pair in which the native foundry passivation layer is used as an ion sensitive layer. The pH sensor has 10 bit resolution with 65.8 LSB/pH sensitivity, while consuming only 0.72 nW at 1 sample/s, improving an overall figure of merit (FoM) that accounts for power, sampling frequency, and sensitivity by > 4000×.