16 May 2003 Noise calculation model for high-gain column amplifiers of CMOS image sensors
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Abstract
One of the important features in CMOS image sensors regarding high sensitivity is that the random readout noise can be better than that of the CCD, if the property of narrow noise bandwidth in CMOS active pixel sensors is effectively used. This is especially important for mega-pixel video-rate image sensors. To meet the requirement, the use of high-gain amplifier at the column of the CMOS imager is effective, because the noise due to wideband amplifier at the output of the image sensor can be relatively reduced. However, it has not been clarified how much the column amplifier can contribute to the noise reduction effect. In this paper, we present a noise calculation model of a switched-capacitor type column amplifier. The total noise consists of a noise component due to the noise charge sampled and held at the charge summation node of the amplifier and transferred to the output, and a noise component directly fluctuates the S/H stage at the output of the column amplifier. The analytically calculated noise has well agreement with that of the simulation results using a circuit simulator.
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Shoji Kawahito, Nobuhiro Kawai, "Noise calculation model for high-gain column amplifiers of CMOS image sensors", Proc. SPIE 5017, Sensors and Camera Systems for Scientific, Industrial, and Digital Photography Applications IV, (16 May 2003); doi: 10.1117/12.479713; https://doi.org/10.1117/12.479713
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