Potentiometric Sensor Circuit Design for Electronic Tongue System

• Main Authors: Tai-Tsun Liu, 劉泰村
• Other Authors: Wen-Yaw Chung
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/60937393499616632925

碩士 === 中原大學 === 電子工程研究所 === 96 === Ion-Sensitive Field Effect Transistor (ISFET) has been developed for almost forty years. In order to improve the performance of ISFET, as the research has showed, the effect of temperature, time drift and hysteresis should be overcome. Therefore, developing different compensation method on ISFETS is still a hot topic today that requires further research. The aim of this thesis is to overcome the effect of temperature on ISFET and to introduce a readout circuit with temperature-sensing and temperature compensation through the design and application of temperature sensor. The major circuits in this study include a modified VT extractor, a depletion-type MOSFET temperature sensing-circuit, an extractor-type readout circuit, a VT extractors based readout circuit of ISFET with temperature compensation, and a voltage regulator with a high stability and low temperature coefficient of frequency (TCF) of 1.65V. Further, through measuring the real chip, the best design of temperature-sensing circuit is proposed and discussed. The circuit proposed in this study dissipates a power as low as 889.3μW. The sensitivity reaches 54mV/pH, and the temperature coefficient before and after the temperature compensation is 4.01mV/℃ and 0.02mV/℃. In addition, a 1.65V voltage regulator’s total power consumption is 91.642μW, and the coefficient of temperature is 4.847ppm/℃.