Science Publishing Group
A current-mode image sensor architecture using a linear-logarithmic pixel in order to improve the dynamic range is presented. The pixel cell is based on a 3T active pixel structure with a PMOS readout transistor in the linear region of operation and a PMOS reset transistor that allows for a linear-logarithmic response. An intra-scene dynamic range of 90dB is obtained with a pixel fill factor of 37%. The readout circuit is composed of a first-generation current conveyor, a current memory employed as a delta reset sampling unit, a differential amplifier used as an integrator and a dynamic comparator. The pixel response operating mode is determined in the column readout.