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Faculty of Science, University of Brunei Darussalam, Brunei Darussalam   
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IJIEE 2013 Vol.3(2): 141-143 ISSN: 2010-3719
DOI: 10.7763/IJIEE.2013.V3.284

A New Method for Current Differential ISFET/REFET Readout Circuit

Taksin Nobpakoon, Wanchai Pijitrojana, and Amporn Poyai
Abstract—This paper presents a new differential current mode readout circuit for ion sensitive field effect transistor (ISFET) to be used as a pH sensor. The circuit used only two MOSFETs to provide current differential pairs result in simplification and very small circuit. It provides a linear sensitivity to pH over a wide range (pH 2-12) which is 25.6 μA/pH with power dissipation of 937.6 μW at 27oC. The circuit is operating in differential mode, reference field effect transistor (REFET) is provided to compensate environment conditions. Temperature compensation in a range of 22-32oC is investigated. It can be well compensated output varying. Simulation results validate the performance of the circuit.

Index Terms—ISFET readout circuit, MOSFET differential pairs, current mode, small circuit

Taksin Nobpakoon and Wanchai Pijitrojana are with the Electrical and Computer Engineering Department Faculty of Engineering, Thammasat University 99 Moo 18, Klongneung, Klonglaung, Pathumthani, Thailand, 12120. Amporn Poyai is with Thai Microelectronics Center (TMEC) National Electronics and Computer Technology Center 51/4 Moo 1, Wangtakien, Muang, Chachoengsao, Thailand, 24000 (e-mail: pimpud@hotmail.com).

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Cite: Taksin Nobpakoon, Wanchai Pijitrojana, and Amporn Poyai, "A New Method for Current Differential ISFET/REFET Readout Circuit," International Journal of Information and Electronics Engineering vol. 3, no. 2, pp. 141-143, 2013.

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