An integrated CMOS optical detector for chemical and biological sensors
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The design and fabrication of a CMOS based optical sensor with integrated LED driver and a surrounding phototransistor (photo cell) array as a detector is presented. The chip is designed so that a thin film GaN LED can be flip chip bonded with the driver circuitry on the silicon wafer (chip pad). The design of the electronics for driving the LED, with the appropriate voltage and current, from the CMOS chip is reported. This simple system is intended to be used for a fluorescence based chemical/biological sensor. In this system, GaN LED source will be used to generate fluorescence from a tagged chemical/biological sensing element. The resulting fluorescence is then captured by the array of phototransistor cells and the photocurrent is converted into a suitable voltage level for recording of the data. The designed chip was fabricated on a standard 40 pin pad frame from the MOSIS foundry in AMI 1.5 μ m technology. The operation of the resulting chip was verified and the results reported in this thesis.