An Electronic Tongue System Design Using Ion Sensitive Field Effect Transistors and Their Interfacing Circuit Techniques

This paper proposes an electronic tongue system design using ion sensitive field effect transistors (ISFETs), extended-gate FET (EGFET) and their interfacing circuit techniques. Bridge-type constant voltage, constant current, and temperature compensation circuitries have all been developed for ISFET to sense hydrogen and chloride ions for water quality monitoring applications. This design offers a sensitivity of over 54 mV/pH and an improved temperature coefficient (T.C.) of 0.02 mV/degC; in addition, a sensitivity of 43 mV/pCl can be achieved by using a proposed extended-gate FET with a mixed polyvinyl chloride (PVC), chloride ionophore III (ETH9033) and lipophylic salt on the indium-tin-oxide (ITO)/glass substrate.