Programmable calibration circuit for a MIM-ISFET device

A programmable calibration circuit for sensors is proposed in this paper, which carries out an offset compensation by adding an appropriate correction factor to the transfer function of each sensor. The circuit was designed for a specific sensor structure, a MIM-ISFET, which was modeled in HSpice. The proposed scheme reduces the offset error due to process variations of both the sensor and the interface circuit from 13% to 2% at the minumim pH level and from 13% to 4% in the whole sensing range. The circuit was designed in a 0.18μm standard CMOS process, occupies an area of 115 × 62 μm² and consumes 1.6mW.