A packaged limiting amplifier with data rates of 20-Gb/s

We designed and fabricated a wide-band limiting amplifier module using AlGa As/GaAs heterojunction bipolar transistors (HBTs) for 20-Gb/s optical commu nication links, and characterized its performances. Circuit design and simu lation were carried out by PSPICE and LIBRA. A typical AlGaAs/GaAs HBTs wit h an emitter area of 1.5 x 10 mu m(2), used for the limiting amplifier, sho wed the peak cutoff and maximum oscillation frequencies of 74 GHz and 115 G Hz, respectively. Fabricated limiting amplifier demonstrated a very wide ba ndwidth of DC similar to 17.5 GHz from on-wafer measurement. Ceramic- and m etal-packaged limiting amplifier showed a good eye opening, an output volta ge swing of 800 mV(p.p), and a rise/fall time of 30 ps, measured at the dat a rates of 20-Gb/s. It demonstrates that the high frequency limiting amplif ier for the 20 Gbps optical communication system can be realized using the optimized AlGaAs/GaAs HBTs if the parasitic effects are carefully considere d in designing the high speed IC's.