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Dissertation 12-17-2018.pdf (6.36 MB)

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Fully-Integrated CMOS pH, Electrical Conductivity, And Temperature Sensing System

Asgari, Mohammadreza
http://rave.ohiolink.edu/etdc/view?acc_num=akron1545054508912344

Abstract Details

2018, Doctor of Philosophy, University of Akron, Electrical Engineering.
This work presents a fully-integrated multi-sensor system based on CMOS technology that contains pH, electrical conductivity (EC), and temperature sensors, as well as an extended-counting analog-to-digital converter (EC-ADC). The pH sensor is implemented using an ion-sensitive field-effect transistor (ISFET) where two low-power, compact pH readout circuits have been designed to overcome the nonidealities of ISFETs. In addition, a novel electrode structure for the EC sensor has been implemented, which eliminates the conventional post-processing steps, thus reducing the cost and fabrication difficulties. Using different frequencies generated by a variable frequency oscillator, the detection range of the proposed EC sensor spans three orders of magnitude, from 20 µS/cm to 10 mS/cm. Furthermore, a complementary to absolute temperature (CTAT) current source with diode-connected transistors was used as the temperature sensor. The measurement range is from 18◦C to 35◦C. The core area, including all three sensors and readout circuits is 2.1 mm2. The EC-ADC is a combination of an incremental sigma-delta and a time-mode ADC. By sharing the OTA and the comparator between two ADCs, the implemented circuit allows the smallest core area amongst state-of-the-art ADCs with similar resolution and bandwidth. The core area of the proposed ADC is 0.0625 mm2, and the measured differential nonlinearity (DNL) and integral nonlinearity (INL) are +0.4/-0.4 and +0.84/-0.88 LSB, respectively.
Kye-shin Lee, Dr. (Advisor)
Joan E. Carletta, Dr. (Committee Member)
Ryan C. Toonen, Dr. (Committee Member)
Truyen Van Nguyen, Dr. (Committee Member)
Chelsea Monty, Dr. (Committee Member)
108 p.
Electrical Engineering
Electrical Conductivity, CMOS, pH, Analog-to-digital-converter, ISFET, Wien-bridge oscillator, instrumentation amplifier, Extended-counting

Recommended Citations

Citations

  • Asgari, M. (2018). Fully-Integrated CMOS pH, Electrical Conductivity, And Temperature Sensing System [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1545054508912344

    APA Style (7th edition)

  • Asgari, Mohammadreza. Fully-Integrated CMOS pH, Electrical Conductivity, And Temperature Sensing System. 2018. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1545054508912344.

    MLA Style (8th edition)

  • Asgari, Mohammadreza. "Fully-Integrated CMOS pH, Electrical Conductivity, And Temperature Sensing System." Doctoral dissertation, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1545054508912344

    Chicago Manual of Style (17th edition)

akron1545054508912344
312
© 2018, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.