Integration of ISFETs in biochemical SOC (System on a Chip) is one of today’s challenges.This article presents a full integration of micro-sensor and readout circuit containing ISFET/REFET (reference FET) pair

ISFET/REFET amplifiers

bias current generator

band-gap reference

as well as a reference electrode structure

all integrated on the same chip based on CMOS technology.The sensor chip is fabricated in a standard 0.35μm CMOS process (Chartered Semiconductor

Singapore) and operates at 3.3V.The extra post processing steps have been developed for ISFET which can work in either linear or saturation region by programmable control.Finally pH response experiments have been carried out and the measurement system achieves 53 mV/pH sensitivity and the enhanced linearity.