| Summary: | 碩士 === 中原大學 === 電子工程研究所 === 91 === Due to the advantage of compatible with CMOS technology, ISFET sensor integrated with signal processing on a monolith has been proved to work. Investigations have demonstrated that ISFET exist a large thermal instability, which leads to inaccuracy measurement. So to develop different compensation method on ISFETs, is already a hot research topic today.
The major objective of this thesis is to discuss the design and application of temperature sensor. In order to have the capability to integrate with ISFET and signal processing, the adopted scheme of the temperature sensor can be implemented with CMOS technology. The major circuits include threshold voltage extractor as temperature sensor, temperature sensor readout circuit, bridge-type floating source ISFET readout circuit. Further, the thermal effect of ISFET and compensation method is also present.
The measured result shows the sensitivity of the thermal sensor readout circuit is 20mV/℃. To co-operate with ISFET, the limitation temperature range between 0℃~50℃. The accuracy is ±2.3℃. Further, with a 5V power supply, the rail-to-rail operational amplifier presents a DC gain of 95dB, offset voltage of 6.4mV and rail-to-rail common-mode input voltage range and voltage output swing. Between standard buffer solutions of pH2 to pH12, the bridge-type floating source ISFET readout circuit base on rail-to-rail amplifier has a sensitivity of 53mV/pH.
In order to verify the thermal effect of ISFET, the simulation of the behavior model of ISFET and the proposed temperature sensor are presented. In the pH7 solution, the temperature coefficients before and after the compensation are 0.9mV/℃ and 0.03mV/℃ respectively.
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