Variable-Dynamic-Range Complementary Metal-Oxide-Semiconductor Image Sensor with Gate/Body-Tied Metal Oxide Silicon Field Effect Transistor-Type Photodetector Using Feedback Structure

In this paper, a new pixel structure for wide-dynamic-range imaging applications is proposed using a feedback mechanism. The pixel is based on a 3-transistor (3-Tr) active pixel sensor (APS) with a gate/body-tied (GBT) p-channel metal oxide silicon field-effect transistor (PMOSFET)-based photodetector. The proposed APS is designed and fabricated using a 0.35 mu m 2-poly 4-metal standard complementary metal-oxide-semiconductor (CMOS) technology, and its characteristics are simulated and measured. The pixel consists of a conventional 3-Tr APS with a GBT photodetector and an additional NMOSFET switch. The GBT photodetector is formed using a PMOSFET with a floating gate connected to an n-well and a transfer gate. The new pixel has a tunable dynamic range achieved by adjusting the applied reference voltage level and its duration. Although the pixel size is increased by 69%, the dynamic range is significantly extended to a maximum of 360% by feedback of the output voltage of each pixel.