High efficiency 15–500MHz wideband cascode GaN HEMT MMIC amplifiers

Two broadband VHF MMIC power amplifiers using GaN HEMT transistors are described in this paper. The first circuit exhibits a PAE ranging from 85% to 51% in the 15MHz - 500MHz bandwidth. The second circuit is a self-biased design and demonstrates a peak PAE of 75% at 100MHz for 13.5W output power in a similar bandwidth. The self biased topology enables a higher bias voltage and therefore higher output power. The 3.3 decade bandwidth operation is accomplished by choosing the device size to match the 50-Ω load thus avoiding any additional matching circuit. The results in this paper demonstrate the usefulness of GaN on SiC technology at VHF/UHF frequencies with fully integrated circuits operating at high output power and efficiency.