ISFET-BASED MEASURING DEVICE AND METHOD FOR FABRICATING THE ISFET USED THEREIN

摘要

The measuring device (10) comprises an ISFET (12) used as a chemically selective ion sensor, a reference electrode (20) positioned adjacent the ISFET (12), an amplifier (22) coupled to the ISFET and control/correction circuitry (30) coupled to the ISFET (12), to the reference electrode (20) and to the amplifier (22). The control/correction circuitry (30) is operable to maintain the drain-source current IDS of the ISFET (12) at a constant value and to correct drift effects of the ISFET (12) on the basis of the logarithmic equation: .DELTA.vp = A 1n(t/to +1) where: .DELTA.Vp = potential drift A = scale factor for drift and amplitude to = time constant defining the dependence on time t = time during which the sensor is operative in the event of continuous operation.