Reconfigurable CMOS Image Sensor Design with Built-In Correlated Double Sampling

We propose a CMOS image sensor pixel readout method that eliminates the need for external correlated double sampling circuit that is used in existing CMOS active pixel sensor (APS) design. The pixel transistor count in the proposed design is equal to the standard APS thus retaining high fill factor. The design employs reconfigurable differential-input readout amplifier that may be used in both the reset and the readout phases of the image sensor operation. In the proposed method, the DC offset is removed, flicker noise is differentiated, and reset noise is greatly reduced by employing the amplifier in an active reset configuration. Gain related fixed pattern noise (FPN) is also reduced by higher open-loop gain of the differential amplifier. We present analysis and simulations of the proposed reconfigurable active pixel sensor (RAPS) design in a standard 0.35 um CMOS process operating from a 3.3 V power supply.