Hybrid active pixel sensor with high-sensitivity and extended dynamic range

This paper presents a hybrid active pixel sensor (HAPS) with high-sensitivity and extended dynamic range without any complex circuit. The photodetector (PD) of the proposed HAPS is composed of a gate/body-tied (GBT) PD for high-sensitivity and a conventional n-well/p-sub PD on the same focal plane for attaining normal image. The gain of the GBT PD is a hundred-times larger compared to the conventional n-well/p-sub PD. The structure of the proposed APS is similar to the conventional 3-transistor APS. Only two transistors are added for selecting each PD (GBT PD and n-well/p-sub PD). Adding the two transfer switches allows to have two modes: the high-sensitivity mode for low-light level detection and the normal mode for higher image quality. In order to reduce pixel size of the proposed APS, the row select transistor is eliminated. Dynamic range of the proposed APS is increased to approximately 86 dB. Its pixel size is 10 μm² for testing pixel performance. The proposed APS is being fabricated by using 1-poly 6-metal 0.18 μm standard CMOS technology.