International Journal of Information and Electronics Engineering
The Ion Sensitive Field Effect Transistor (ISFET) is a chemically sensitive field effect transistor was introduced by the researchers in 1970s. The ISFET is similar to a MOSFET, except that the gate of MOSFET is replaced by an ion sensitive membrane exposed to an aqueous solution. They present schematic diagram of ISFET and MOSFET. The membrane is sensitive to hydrogen ions in the test solution when there is a change in hydrogen ions on the membrane surface, a change in the potential on the surface will occur and it is correlated to solution pH, causes a modulation in the ISFETs threshold voltage.