A CMOS linear voltage/current dual-mode imager
Zheng Yang; Gruev, V.; Van der Spiegel, J.
Circuits and Systems, 2006. ISCAS 2006. Proceedings. 2006 IEEE International Symposium on
Volume , Issue , 0-0 0 Page(s):4 pp. -
Digital Object Identifier 10.1109/ISCAS.2006.1693399
Summary:We present a CMOS image sensor capable of both voltage- and current-mode operations. Each pixel on the imager has a single transistor acting as either source follower for voltage readout, or transconductor for current readout. The two modes share the same readout lines, but have their own correlated double sampling (CDS) units for noise suppression. We also propose a novel current-mode readout technique using a velocity-saturated short-channel transistor, which achieves high linearity. The 300times200 image array is a mixture of 3 types of pixels with identical photodiodes and access switches; while the readout transistors are sized for their designated mode of operation. This ensures a fair comparison on the performance of the different modes
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