A 3-V CMOS optical preamplifier with DC photocurrent rejection

This paper describes a CMOS optical preamplifier suitable for free-space, infrared wireless communications. The design is differential for improved power supply noise rejection, and an active cancellation scheme is used for eliminating dc photocurrents that are generated by ambient light. Making use of a 0.35-/spl mu/m CMOS process, the preamplifier provides a transimpedance gain of 20 k/spl Omega/ over a bandwidth from 1 MHz to 100 MHz and achieves 60 dB attenuation at dc.