We propose a new circuit for Ion-Sensitive-Field-Effect-Transistors (ISFETs) for pH sensing based on a standard mixed-signal-processor with minimal required external components. The ISFET is controlled by a servo loop in software. The internal ADC is used for feedback. We compare this method with an analog ISFET readout circuit and show their equivalence. The new circuit provides some additional features, such as run time configurable operating point and channel type settings. The integrated MCU can perform calibration and sensor diagnosis functionality and eases the integration in other systems and parallel operation of many units with its digital interfaces.      «

We propose a new circuit for Ion-Sensitive-Field-Effect-Transistors (ISFETs) for pH sensing based on a standard mixed-signal-processor with minimal required external components. The ISFET is controlled by a servo loop in software. The internal ADC is used for feedback. We compare this method with an analog ISFET readout circuit and show their equivalence. The new circuit provides some additional features, such as run time configurable operating point and channel type settings. The integrated MCU...     »