The mfluence of optical radlatlon on the MOSFET threshold voltage has been mvestlgated theoretically as well as experimentally For conventlonal MOSFETs the influence 1s neghglble, but for open-gate FET-based sensors, such as the ISFET, optIcal radiation can cause a considerable threshold voltage shift An explanation of the threshold voltage shrft due to lllummatlon 1s given, based on the analys...