| 摘要 |
A column current source for an image sensor is disclosed comprising 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; a plurality of current sources each connected to a column of pixels and each current source forming the other half of the current mirror and thereby mirroring the reference current source, wherein the current sources are connected to a first common node, wherein a resistor means connected between the first common node and a second common node; one or more further resistor means connected in series between the second common node and the drain of the transistor; and two or more switch means selectively operable to short circuit the resistor means or the or each further resistor means so as to allow more than two levels of current to be provided by the plurality of current sources. By enabling the current source to provide more than one current level, the current consumption of the image sensor can be optimised for mobile devices.
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