20 Gb/s digital SSIs using AlGaAs/GaAs heterojunction bipolar transistors for future optical transmission systems

Design principles for achieving good eye opening and circuit optimization to extract high performance from AlGaAs/GaAs heterojunction bipolar transistor (HBT) devices are described. Using the circuit techniques and HBTs with an f/sub T/ of 70 GHz and an f/sub max/ of 50 GHz, four kinds of SSIs are developed for future optical transmission systems. High-bit-rate operation of over 20 Gb/s (26 GHz toggle flip-flop, 20 Gb/s decision circuit, 20 Gb/s EXCLUSIVE OR/NOR gate, and 28 Gb/s selector IC), extremely fast rise and fall times (20-80%) of 20 and 14 ps, respectively, and good eye opening are obtained. In addition, potential performance gains that might be realized through advanced circuit and device design are appraised, and throughputs as fast as 40 Gb/s are predicted.<
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