Small area optical inputs for high speed CMOS circuits

Compact and fast photoreceivers with on-chip photodiodes in standard CMOS technology have been developed as optical inputs for digital circuits. The time performance of different photodiodes and current/voltage converters has been investigated and optimized by simulations and experiments. The best performance with periodic signals of more than 250 MHz was found for a current comparator circuit with a statically supplied reference photodiode. The total chip area required for the complete optical receiver was less than 70×70 μm²