A New Method for Current Differential ISFET/REFET Readout Circuit

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.

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