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Proceedings Paper

CMOS active pixel sensor achieving 90-dB dynamic range with column-level active reset
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Paper Abstract

A CMOS active pixel sensor array using column-level active reset has been fabricated and tested. Column-level active reset requires one additional transistor per pixel, bringing the total to 4, and a per-column op-amp. The added transistor per pixel controls the gate of the reset transistor. There are two important feedback mechanisms in active reset. The first is the amplification by the Miller effect of the effective capacitance on the photodiode during reset, hence reducing kT/C noise. The second is the control of the resetting current via modulation of the transconductance of the reset switch. The level of noise reduction is comparable to, or may exceed, what true correlated double sampling can achieve. Readout noise of 44 microvolts and a dynamic range of 90 dB (15 bits), rms, has been measured. Room temperature noise as low as 5.1 electrons, rms, referred back to the photodiode node, has been measured on small photodiode pixels (5.8 fF capacitance). This compares to 38.3 electrons when measured with a standard “hard” reset, for a factor of 7.6 improvement. Row and column fixed pattern noise were also improved by up to a factor of 21, going from 1% for both to 0.048% and 0.27%, respectively.

Paper Details

Date Published: 7 June 2004
PDF: 12 pages
Proc. SPIE 5301, Sensors and Camera Systems for Scientific, Industrial, and Digital Photography Applications V, (7 June 2004); doi: 10.1117/12.527111
Show Author Affiliations
Yandong Chen, Univ. of California/Irvine (United States)
Stuart Kleinfelder, Univ. of California/Irvine (United States)

Published in SPIE Proceedings Vol. 5301:
Sensors and Camera Systems for Scientific, Industrial, and Digital Photography Applications V
Nitin Sampat; Morley M. Blouke; Ricardo J. Motta, Editor(s)

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