50-GHZ-BANDWIDTH BASEBAND AMPLIFIERS USING GAAS-BASED HBTS

Baseband amplifiers of 50 GHz, using highperformance AlGaAs/InGaAs HBT 's with regrown base contacts, have been demonstrated, The transimpeda nce amplifier achieved a bandwidth of 50.8 GHz with a gain of 11.6 dB. The transimpedance characteristics were of 49.3-GHz bandwidths with a 43.7-dB Ohm transimpedance gain. The resistive and mirror Darlington feedback amplifiers, respectively, achieved a bandwidth of 54.7 GHz wi th a gain of 8.2 dB and a bandwidth of more than 60.0 GHz with a gain of 6.3 dB, To date, these are the widest bandwidths reported for lumpe d-circuit-design amplifiers. These results suggest the great potential of these amplifiers for use in future optical communication, microwav e and millimeter-wave applications.