Importance

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Abstract

An active pixel sensor cell that will convert a quantum of light energy to an electronic signal representing the amplitude of the quantum of light energy is disclosed. The active pixel sensor cell is immune to image blooming and has a reset operation to reduce image lag. An active pixel sensor has a photodiode, a bipolar transistor and a MOS transistor. The photodiode has a cathode connected to a power supply voltage source and an anode to the MOS transistor. The quantum of light energy will impinge upon the anode and generate electric charges within the photodiode. The MOS transistor will prevent the image blooming by disconnecting the anode of the photodiode from the base of the bipolar transistor and connecting the anode of the photodiode to MOS transistor to allow the electric charges in the photodiode to flow through the MOS transistor. The bipolar transistor will amplify the electrical charges to create the electronic signal. The active pixel sensor further includes a parasitic MOS transistor. The drain of the parasitic MOS transistor is the anode of the photodiode, the source is the anode of the photodiode of an adjacent active pixel sensors of a row of active pixel sensors within an array of active pixel sensors. When the parasitic MOS transistor is turned on by a reset circuit, it will reset the anode of the photodiode to the same level as that of other photodiodes in a row to reduce image lag on the active pixel sensor.

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First Claim