Operational of ISFET as a pH Sensor by Using Signal Modulated Reference Electrode

As an alternative to miniaturize sensor size, study on Ion Sensitive Field Effect Transistor (ISFET) as a pH sensor by applying AC modulation signal to the reference electrode is presented. The small size of solid state reference electrode was fabricated onto the silicon. The reference electrode was developed by using metal and covered with an insulator. An AC modulating signal, from 10 Hz up to 1 MHz is used to study the biasing effect to the reference electrode and subsequently to modulate ISFET channel for output. From the experimental result, ISFET was successfully responding as a pH sensor at low frequency of AC modulating signal.