ISFET based chemical Gilbert cell

Abstract

An ion-sensitive field effect transistor (ISFET) based chemical Gilbert cell is presented, capable of differential measurement of pH signals during thermocycling reactions. The proposed circuit is capable of measuring the difference between two reaction chambers allowing stable drift reduction. Implemented in a typical 0.35 µm CMOS process, the resulting topology has a tunable gain of up to 40 dB, is temperature stable, with a variation of just 0.7% within the range of 0 to 100°C and achieves a low power consumption of 198 nW.