Multi-decade GaN HEMT Cascode-distributed power amplifier with baseband performance

This paper reports on multi-decade bandwidth GaN HEMT Cascode-distributed power amplifier designs which achieve performance from base-band to over 20 GHz. The GaN MMICs are based on a 0.2um AlGaN/GaN low noise T-gate HEMT technology with an fT ∼ 75 GHz. To increase the MMIC power capability of this low noise GaN technology, a cascode DA design approach was employed which can operate at twice the recommended Vds voltage. The resulting amplifiers achieve 1–4 Watts of saturated CW power from 100MHz to over 20GHz at an operating voltage of 30V. Typical OIP3 ≫ 40 dBm and NF of 3 dB were also achieved. Compared to equivalent designs in a similar 0.15um GaAs PHEMT low noise technology fabricated in the same foundry, these multi-decade GaN HEMT MMIC DAs obtain 6 dB higher output power and 5.8–6.6dB higher OIP3 while achieving comparable gain, noise figure, and bandwidth. These are believed to be the first multi-decade GaN power distributed amplifiers that have been demonstrated and can enable future ultra-wideband frequency agile and software defined radio systems that require baseband to microwave frequency operation.