ISFET incorporated in a differential amplifier

Keiji Tsukada, Takuya Maruizumi, Hiroyuki Miyagi

Research output: Contribution to journalArticlepeer-review


The output of the ISFET (Ion Sensitive Field Effect Transistor) was obtained as a voltage signal. To achieve the temperature compensation, a differential amplifier composed of ISFET and MOSFET was fabricated. For integration, the process and circuit designs for the ISFET and MOSFET were done carefully by considering both the device fabrication process and the electrical properties of the device. Polycrystalline silicon was used for the connection between the devices and the MOSFET gate electrode. The entire device surface was covered with Si3N4/SiO2 to ensure the waterproof properties of the device. As a result, the MOSFET could be located near the ISFET and both FETs could be processed in the same manner. The fabricated ISFET could produce the voltage signal in accordance with the change in the gate membrane potential of the ISFET. The sensitivity of the device was 49 mV/pH. In addition, temperature compensation in the ISFET was achieved and the temperature coefficient was −0.8 mV/°C.

Original languageEnglish
Pages (from-to)82-88
Number of pages7
JournalElectronics and Communications in Japan (Part II: Electronics)
Issue number3
Publication statusPublished - 1988
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Computer Networks and Communications
  • Electrical and Electronic Engineering


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