ANALYSIS OF PHOTOELECTRIC CONVERSION CHARACTERISTICS UNDER KNEE CONTROL OPERATION FOR CCD IMAGERS

A high-light signal suppression operation, knee control operation, was evaluated in order to apply to a STACK-CCD of 2/3-in 2 M-pixel high d efinition television (HDTV) imager overlaid with an amorphous silicon photoconversion layer, A smooth bent was observed in the measured phot oconversion characteristics near a knee point, It was analyzed theoret ically by applying a subthreshold current of the MOSFET in weak invers ion for skimming excess charges and reading out signal charges through a field shift gate, The calculated curve showed good agreement with t he measured curve, Effectiveness of the knee control operation using t he field shift gate was shown experimentally and theoretically over th at using a conventional vertical overflow drain for IT-CCD imagers,