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Circuits for ISFET

Circuits for ISFET. Various circuits commonly used in sensors. Read-out circuit for ISFET. Ref: Sensors and Actuators B: Chemical Volume: 75, Issue: 1-2, April 30, 2001. pp. 36-42. ISFET Characteristics. Various gate materials.

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Circuits for ISFET

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  1. Circuits for ISFET

  2. Various circuits commonly used in sensors

  3. Read-out circuit for ISFET Ref: Sensors and Actuators B: Chemical Volume: 75, Issue: 1-2, April 30, 2001. pp. 36-42

  4. ISFET Characteristics

  5. Various gate materials • The selectivity and chemical sensitivity of the ISFET are completely controlled by the properties of the electrolyte/insulator interface. • Other inorganic gate materials for pH sensors like Al2O3, Si3N4 and Ta2O5 have overall better properties than SiO2 with high sensitivity (high pH response), low hysteresis and low drift.

  6. Disadvantages of ISFET • Large drift (long-term drift and thermal drift) requires stringent encapsulation of the chip edges and binding leads • Mechanism for the long-term drift is not clear • Although the amplification properties of the transistor in these devices seem very attractive for sensing chemicals, the vulnerability of the insulating membrane to environmental poisoning and subsequent transistor breakdown has prevented the ISFET from gaining popularity in commercial markets.

  7. ISFET Commercial Examples

  8. Commercial examples • Mettler Toledo commercial ISFET • Recently developed, unbreakable solid-state ISFET pH electrode • Intended for use in the food processing industry, where the possibility and consequences of fractured glass present a highly dangerous threat. • It complies with 3-A sanitary standards, has been tested to EHEDG requirements and is in compliance with FDA regulations.

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