Column current source

Details Column current source Column current source

2007-12-28

2010-02-09

Epps, Georgia Y (Department: 2878)

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

C250S2140RC, C250S2140SW, C348S308000, C257S291000

Reexamination Certificate

active

07659500

ABSTRACT:
A column current source for an image sensor includes an array of pixels arranged in rows and columns, a reference current source, a transistor connected as a source follower to the reference current source and forming one half of a current mirror, and a plurality of current sources each connected to a column of pixels and with each current source forming the other half of the current mirror, thereby mirroring the reference current source. The current sources are connected to a first common node. A resistor is connected between the first common node and a second common node. One or more resistors are connected in series between the second common node and the transistor drain, and two or more switches are selectively operable to short circuit the resistors allowing the current sources to provide more than two current levels, thereby optimizing the image sensor current consumption for mobile devices.

REFERENCES:
patent: 6437309 (2002-08-01), Kozuka et al.
patent: 6897429 (2005-05-01), Turner et al.
patent: 2002/0057355 (2002-05-01), Sakuragi
patent: 1 596 578 (2005-11-01), None
patent: 5207374 (1993-08-01), None

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