A 2-50 GHz InAlAs/InGaAs-InP HBT distributed amplifier

Here we report on a 2-50 GHz InAlAs/InGaAs-InP HBT Distributed Amplifier (DA) which demonstrates the highest frequency of operation so far reported for a wideband HBT amplifier and is a 10 GHz (25%) improvement over previous state-of-the-art. The amplifier features 1/spl times/4 /spl mu/m/sup 2/ single-emitter HBTs with a base under-cut structure for reducing the device's collector-base capacitance C/sub bc/, resulting in as much as a 20% improvement in device f/sub max/ performance. The MMIC is a 5-section coplanar waveguide distributed amplifier design which employs HBT cascode devices. Previous work using non-undercut HBTs has resulted in 5.5 dB gain and 2-32 GHz BW performance. In the present work, the HBT DA obtains a peak gain of 6.3 dB with a bandwidth beyond 50 GHz while operating from a 4 V supply and consuming only 89 mW of DC power. The gain is 4.1 dB at 30 GHz, 3.9 dB at 40 GHz and 4 dB at 50 GHz. An open circuit transimpedance of 45 dB-/spl Omega/ calculated from S-parameters is achieved with an upper band edge of >50 GHz. The corresponding effective 5O-/spl Omega/ loaded transimpedance is 39.2 dB-/spl Omega/ also has an upper band edge of >50 GHz. The wideband gain and transimpedance results here benchmark the highest bandwidths so far recorded for either HBT or BJT amplifiers and suggests the capability of InAlAs/InGaAs HBTs for millimeter-wave and high data rate (40 Gbps) IC applications.