Image sensor and pixel that has variable capacitance output or floating node

摘要

A pixel and image sensor formed in accordance with the present invention has two modes of operation: a 3T mode and a 4T mode. The present invention switches from a 3T to a 4T mode based upon the amount of illumination on the image sensor. The amount of illumination on the image sensor can be determined in a variety of ways. Once the level of illumination is determined, a decision is made by comparing the level of illumination to a threshold whether to operate in 3T mode (for high illumination) or 4T (for low illumination) mode.