Active Broadband Termination for Distributed Amplifiers Using a 45-nm BiCMOS SOI Process

An active-bias termination (ABT) is proposed to generate an electronically tunable broadband load for a distributed amplifier (DA). The ABT utilizes a shunt-feedback transimpedance stage that simultaneously produces a fixed load impedance over a broad frequency range with potentially lower noise contribution. Two DAs are fabricated based on a hybrid cascode cell for low noise measure to compare the ability of the ABT to realize lower gain ripple and noise figure (NF) compared to a resistive termination (RT). The DAs achieve 25 dB of average gain over 150 GHz of bandwidth (BW) with a peak output power of 14.9 dBm and a 7.8-dB minimum NF. Modulated 15-Gbaud 64-QAM signals are also demonstrated on both types of DAs with 10.0 dBm of average output power and 6.5% EVM. This work also exhibits the highest single-frequency complex modulated measurement with a 17.5-Gbaud 64-QAM (105 Gbps) waveform.