A self-contained CMOS integrated pH sensor

The authors report the design and evaluation of a self-contained CMOS integrated ISFET (ion-sensitive field effect transistor) pH sensor. They demonstrate two technological solutions for the implementation of a microelectronic ISFET pH sensor: (1) a standard-CMOS-compatible process for fabricating the ISFET and CMOS analog circuits on the same chip has been developed and (2) the electrical reference contact to the electrolyte has been integrated on the same chip as the ISFET by a differential sensing circuit technique.<<ETX>>