Linear-Logarithmic Wide-Dynamic-Range Active Pixel Sensor with Negative Feedback Structure Using Gate/Body-Tied Photodetector with an Overlapping Control Gate

In this paper, we present a linear-logarithmic wide-dynamic-range complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) that uses a gate/body-tied (GBT) photodetector (PD) with an overlapping control gate. The amplifying photocurrent of the PD is 100-fold larger than that of a conventional n+/p-sub PD. Although the GBT PD with an overlapping control gate has high sensitivity, it is difficult to apply this PD to the structure of an APS owing to its very narrow dynamic range. Therefore, we proposed a novel APS using an output voltage feedback structure that makes it possible to extend the dynamic range to 101 dB while maintaining high sensitivity under low illumination (below 20 lx). The proposed APS was fabricated using a 0.35-mu m, 2-poly 4-metal standard CMOS process, and its characteristics were evaluated.