An isfet chip suitable to be used in an apparatus comprising a measuring circuit for selectively measuring ions in a liquid

An ISFET chip suitable to be used in an apparatus comprising a measuring circuit for selectively measuring ions in a liquid, said ISFET chip including a source and a drain diffused in bulk of the chip and provided with a source contact element and a drain contact element, as well as provided with means for protection of the ISFET from damage due to the presence of high voltages, having as the protection means an electrode on the chip closely adjacent to the gate region of the ISFET, said electrode taking the form of a metallic ring applied around the gate region of the ISFET.