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 0.2 mum 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 100 MHz to over 20 GHz at an operating voltage of 30 V. Typical OIP3 > 40 dBm and NF of 3 dB were also achieved. Compared to equivalent designs in a similar 0.15 mum GaAs PHEMT low noise technology fabricated in the same foundry, these multi-decade GaN HEMT MMIC DAs obtain 6 dB higher output power and 5.8-6.6 dB 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.