Abstract: A gas sensor which includes a reference electrode deposited on the surface of a pH-sensitive transducer having a gate-insulated field-effect transistor (FET) structure and adjacent a gate region of the FET, the transducer and reference electrode being housed in a flexible tube so that the gate region of the FET is located in an opening provided at the front end of or on the side wall of the tube. Lead wires connected to the FET and to the reference electrode extend along the tube. Between the inner wall of the tube and lead-wire FET bonding part is placed electrical insulation resin filling to stop the tube. A hydrophilic polymer layer containing electrolyte is provided which at least extends over both the FET gate region and a part of the reference electrode. A gas permeable membrane is laid over the polymer layer.

Abstract: An electrical circuitry for use in the measurement of the activity of ions in an electrolyte solution carried out by the use of an ion-sensitive field-effect transistor transducer having a gate or ion sensitive layer, a source and a drain. The measurement is carried out by adjusting the drain current flowing through the field-effect transistor to a predetermined value such that the temperature dependency of the electroconductivity of the channel of the transistor becomes equal to the sum of the temperature dependency of the potential at an interface between a reference electrode and the electrolyte solution and the temperature dependency of the potential at an interface between the ion-sensitive layer and the electrolyte solution.

Abstract: A selective chemical sensitive field-effect transistor device for use in detection and measurement of chemical properties of substances to which the device is exposed is disclosed. The chemical sensitive FET device comprises a semiconductor substrate, at least one pair of spaced apart diffusion layers formed on one surface of the semiconductor substrate and forming source and drain regions, respectively, and a double layer structure consisting of a silicon oxide layer and an electrically insulating layer overlaying the silicon oxide layer. A gate region located on a portion of the surface of the semiconductor substrate between the diffusion layers is overlaid with a chemical selective membrane adapted to interact with certain substances. A method for the manufacture of the above described FET device is also disclosed.

Abstract: A chemical sensitive field effect transistor transducer is provided having a semipermeable membrane on the surface of a chemical selective system overlying an insulated gate field effect transistor. Such a field effect transistor transducer is effective for the measurement of chemical constituents of factory waste water containing micro-particles, saliva or blood containing proteins, etc., where conventional devices give unreliable results.

Abstract: A reference electrode of an insulated gate field effect transistor having the surface of the gate region thereof coated with a hydrophobic organic polymer membrane. Since this reference electrode is much smaller in size than conventional reference electrodes, an integrated measurement system can easily be constructed by using this reference electrode. This measurement system is especially effective for measuring various ions in the living body.

Abstract: A selective chemical sensitive field-effect transistor device for use in detection and measurement of chemical properties of substances to which the device is exposed is disclosed. The chemical sensitive FET device comprises a semiconductor substrate, at least one pair of spaced apart diffusion layers formed on one surface of the semiconductor substrate and forming source and drain regions, respectively, and a double layer structure consisting of a silicon oxide layer and an electrically insulating layer overlaying the silicon oxide layer. A gate region located on a portion of the surface of the semiconductor substrate between the diffusion layers is overlaid with a chemical selective membrane adapted to interact with certain substances. A method for the manufacture of the above described FET device is also disclosed.