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New ISFET interface circuit design with temperature compensation |
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| Authors: | Wen-Yaw Chung Yeong-Tsair Lin Chung-Huang Yang Alfred Krzyskow |
| Affiliation: | a Department of Electronic Engineering, Chung Yuan Christian University, 32023 Chung-Li, Taiwan, ROC b Department of Electronic Engineering, Vanung University of Science and Technology, 32045 Chung-Li, Taiwan, ROC c Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, ul. Trojdena 4, 02-109 Warsaw, Poland |
| Abstract: | An integrated and new interface circuit with temperature compensation has been developed to enhance the ISFET readout circuit stability. The bridge-type floating source circuit suitable for sensor array processing has been proposed to maintain reliable constant drain-source voltage and constant drain current (CVCC) conditions for measuring the threshold voltage variation of ISFET due to the corresponding hydrogen ion concentration in the buffer solution. The proposed circuitry applied to Si3N4 and Al2O3-gate ISFETs demonstrate a variation of the drain current less than 0.1 μA and drain-source voltage less than 1 mV for the buffer solutions with the pH value changed from 2 to 12. In addition, the scaling circuitry with the VT temperature correction unit (extractor) and LABVIEW software are used to compensate the ISFET thermal characteristics. Experimental results show that the temperature dependence of the Si3N4-gate ISFET sensor improved from 8 mV/°C to less than 0.8 mV/°C. |
| Keywords: | Ion sensitive field effect transistor (ISFET) pH sensor Temperature compensation |
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