Patent ID: 8802472
Filing Date: 2014-08-12
Classification: H01L

Abstract:
1. A method for driving a pixel of an image sensor, wherein the pixel includes a source follower JFET configured to receive a signal from a floating diffusion node, the method comprising: addressing the pixel to readout the signal during a readout sequence, wherein the readout sequence includes a reset operation to charge the floating diffusion node to a reset voltage and a transfer operation to charge the floating diffusion node to a pixel voltage corresponding to a photo-generated charge; directing the pixel to a non-readout state at a time after completion of the readout sequence; and providing a predetermined set voltage on the floating diffusion node when the pixel is in the non-readout state; wherein the predetermined set voltage has a magnitude sufficient to forward bias a p-n junction between a gate and drain of the source follower JFET, but insufficient to drive the source follower JFET to an active readout state, and wherein the forward bias of the p-n junction at the predetermined set voltage is sufficient to allow a small current to flow from the floating diffusion node through the p-n junction thereby inhibiting voltage drift of the floating diffusion node from the predetermined set voltage.