Patent attributes
In one aspect of the present invention, a light sensor is provided in the active pixel sensor cell for sensing incident radiation. The voltage corresponding to the photon-generated or other radiation-generated charge in the active pixel sensor cell is stored on a storage node via a sample-and-hold capacitor. Additional elements, such as source-follower transistors, may reside between the sensing element and the sample-and-hold capacitor. The signal is read via a readout source-follower (RSF) transistor. The readout source-follower drain is connected to the row select switch while its drain is connected to the output node on the column output bus. This configuration couples the storage node to the gate-source capacitance of the readout source-follower transistor. This allows the voltage on the storage node to increase proportionally to the increase in voltage on the readout node when the row select is closed and thus enables the drain current to flow through the RSF to the column output bus.
