An ISFET Interface Circuitry for Biomedical Applications

The ion-selective field effective transistor has features of rapid reaction time, high sensitivity, batch processing, small size and single chip integration. It can be implemented by CMOS technology. These advantages make it the first choice for VLSI electrochemistry bio-inspired applications. In order to capture the response of the ISFET sensors, it is necessary for the ISFET to be accompanied by an analogue interface electronic. The important contribution of this paper is to present a readout circuit allowing reduction of influence of body effect. It is applicable to use in ISFET-based microsystems. The proposed circuit shows an enhanced accuracy of pH measurements while maintaining the ISFET being at constant drain-source voltage and current condition, with the reference electrode grounded. Furthermore, the presented scheme permits of improving the temperature dependency, long-term drift with the differential output configuration.