Patent ID: 7936039
Filing Date: 2011-05-03
Classification: H01L,H04N

Abstract:
1. A backside illuminated CMOS image sensor with a front side and a back side, the backside illuminated CMOS sensor comprising: a photosensitive element on the back side, for releasing charge when light strikes the photosensitive element; a photo gate on the front side, the photo gate having a potential well for receiving the released charge from the photosensitive element; a sense diffusion for receiving the released charge from the potential well; a readout circuit coupled to the sense diffusion, for measuring a voltage corresponding to the released charge transferred to the sense diffusion; a drain switch adjacent the photo gate on the front side, for draining excess charge from the photo gate; and comparison circuitry arranged to compare the voltage measured by the readout circuit to a threshold voltage; said readout circuit further arranged to: