A differential ISFET pH sensor

In this paper, we present a simple differential CMOS ISFET based pH sensor. The design uses two different sensing areas. The resulting sensor reduces complexity and power consumption making it suitable for implantable biomedical applications. The design is implemented in a standard 130nm process and the design constraints on sensitivity are explored. Analytical results based on theory show that sensor sensitivity increases with increasing transistor areas, biasing current levels and maximized difference in the two sensing areas. The designed differential single-chip ISFET pH sensor provides satisfactory performance for a 1-14 pH range with power consumption of 1.2 μW for bias current of 1 μA, simple structure, and sensor size of 160 μm × 80 μm.