Modeling of pixel sensors for image systems with VHDL-AMS

The design of mixed signal systems on chip is in a continuous growth these last few years. So the technical progress for systems integration allows the implementation of millions of active or passive pixel sensors (APS or PPS) on a same chip in order to define image matrix (system on chip). It has become crucial for the design of these systems to accurately predict their behavior prior to manufacture. Now the emergence of standard description languages as VHDL-AMS offers an effective and efficient way to describe these multiple domain and mixed-signal electronic systems. The aim of this work is the modeling of pixel sensors (APS and PPS), basic cells of CMOS image systems. Pixel sensors are composed of photodetectors for photogeneration of current and photocircuit for conversion and/or pre amplification of this current. PPS are usually associated to an operational amplifier (OPA). So in this paper the authors present models for each one of these parts and we instantiate them to simulate PPS and APS cells