Design and Topology Considerations for a Family of X-Band GaN Power Amplifier MMICs

Transistor selection and power drive ratio considerations are critical in high power amplifier design. This work reports four high power amplifier MMICs operating at X-band, discusses two-stage and three-stage design approaches for various output power and efficiency goals while investigating the trade-off between them. All of the four MMICs are fabricated using NANOTAM's 0.25 mu m GaN on SiC technology and measured on-wafer. Experimental results show that the first pair of power amplifiers with drive ratios of 1:4 achieve an output power of 13.2-16 W with power-added efficiency between 36.6-46.8%, while the second group of power amplifiers which have more conservative drive ratios of 2:4 are capable of higher output power between 14-18.1 W with lower power-added efficiency of 32.5-38.2%, all recorded at 6 dB gain compression.