A conventional active pixel sensor (APS) uses a source follower (SF) in a pixel as a buffer. This SF is one of the major causes of nonlinearity, sensitivity degradation, and pixel readout noise. The proposed in-pixel comparing APS uses pixel transistors as a part of comparator for a single-slope ADC instead of using them as an SF. The prototype sensor was fabricated using a 0.35-μm 2P3M CMOS process. Experimental results show 15-times linearity improvement, 26% sensitivity enhancement, and 33% noise reduction over the conventional APS.
Bibliographical noteFunding Information:
Manuscript received May 13, 2008; revised August 22, 2008. Current version published November 26, 2008. This work was supported in part by the Ministry of Knowledge Economy (MKE), Korea, under the Information Technology Research Center (ITRC) support program supervised by the Institute for Information Technology Advancement [(IITA); IITA-2008-(C1090-0801-0012)] and in part by Samsung Electronics Co. Ltd. The review of this paper was arranged by Editor J. Tower.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering