Integration of phototransistors in CMOS circuits

A solution for integrating a photosensor in custom-designed digital circuits fabricated using conventional complementary metal-oxide-semiconductor (CMOS) technology is presented. In this approach, by starting with device characterization and parameterization, a method for designing sensor cells is developed. Experimental results obtained from a programmable sensitivity photosensor, such as optical gain, linearity, spectral sensitivity and response delay, are presented. The problem of crosstalk from cell integration in an array is also discussed.