The Operation of an Isfet as an Electronic Device

The conventional ion senwtlve sensors, such as glass membrane electrodes, coated unre electrodes, metal-metal oxide electrodes, etc , convert a non-electrical quantity mto an electrical quantity, which can then be measured wrth approplnate electronic clrcultry connected m senes Unpredictable devlatlons m transducer parameters cannot be controlled m such a measunng system Because the ISFET also has an electrical mput besides the ion-senatlve input, this results m unique apphcatlon posslbllltles, mth consequences for the development of adequate electromc clrcultry In order to obtzun an insight mto this matter, It 1s useful first to understand the electmcal behavlour of a MOSFET, from which the ISFET behavlow can be denved. Based on this theory some electromc design startmg points can be developed for an appropnate ISFET apphcatlon