TFA Image Sensors for Low Light Level Detection

TFA technology, using ASICs coated with amorphous silicon based photo detectors, opens new applications for CMOS image sensors. One particular field of interest is the detection of low light level images with pixel photocurrents in the femtoampere range and below. In this paper we describe the effects of the capacitances on the pixel amplifier, we derive noise values for the detector and the amplifier, and we estimate the gain fixed pattern noise level. An inverter circuit providing a 40-fold increase of the charge conversion gain is presented.