CMOS readout circuitry for ISFET microsystems

CIMP (complementary ISFET/MOSFET pair)—a novel technique for implementation of readout interface in CMOS ISFET-based microsystems is described. This design technique allows body effect elimination, temperature compensation and design simplicity, while maintaining constant biasing of ISFET sensor. Several configurations of CIMP interface provide applicability for array-type sensors. The general concept presentation is followed by a detailed analysis, test results showing 0.1% accuracy and layout implementations in a standard 1.6 μm CMOS technology.