Low-cost MOSFET based pH-sensor Using Ag/AgCl Glass electrodes

A cost-effective pH sensing system using Ag/Agel glass electrode as a pH-sensitive material for a N-channel Metal Oxide Semiconductor Field Effect Transistor (MOSFETIRFZ44N) has been fabricated. The change in pH is evaluated by finding the change in transfer (IDS Vs VGS) and output characteristics (IDS Vs VDS) of a MOSFET. The gate terminal of MOSFET is connected to a glass electrode providing an electrochemical measurement cell in combination with a reference electrode. This paper presents experimental resultson pH-variation of the solution in contact with the glass electrodethat can be sensed by the MOSFE T. The change is studied through the variation in drain current and threshold voltage. At pH 3, threshold voltage is 2.304 V and at pH 12, threshold voltage is 2.789 V which suggests that as pH increases, threshold voltage also increases. Due to their low cost and ease in processing, such devices are possible candidates to be used as versatile, low-cost pH sensors. Research is being carried out with the aim of developing a pH sensor with high sensitivity and low cost.