A high-sensitive digital photosensor using MOS interface-trap charge pumping

Abstract

A high-sensitive CMOS photosensor based on a pulse frequency modulation (PFM) scheme is presented. We propose and demonstrate the high-sensitive PFM photosensor, whose output frequency is proportionate to the incident light intensity, that utilizes MOS interface-trap charge pumping (ITCP) as a frequency-controlled ultralow current. The proposed pixel sensorconsists of only 4 transistors: a transistor as an ultralow current source; a sense amplifier transistor; a selection transistor; and, a reset transistor. The prototype device is fabricated using 0.6-µm standard CMOS technology. High sensitivity 4.0 × 105Hz/(W · m-2), which is larger than two orders of magnitude compared to previous works, wasobtained. © 2004, The Institute of Electronics, Information and Communication Engineers. All rights reserved.