Circuit provides ISFET-sensor bias

摘要

ISFETs (ion-sensitive field-effect transistors) are useful for measuring the acidity of fluids. Accurate measurements require that the ISFET's bias conditions (I_D and V_(DS)) be held constant while the gate is exposed to the fluid under test. The acidity of the fluid changes the channel width, resulting in a gate-source voltage, V_(GS), that is proportional to the fluid's pH. A recently published Design Idea shows a biasing circuit for the ISFET (Reference 1).