This paper describes and evaluates two MMIC broadband high power amplifiers in the frequency band 2-6 GHz in microstrip technology. These amplifiers have scalable output-stage periphery of 4 and 8 mm. The amplifiers are based on 1 mm AlGaN/GaN high electron mobility transistor (HEMT) technology on SiC substrate. They were fabricated in the European foundry SELEX Sistemi Integrati, which has a gate process technology of 0.5 μm. The 4 mm amplifier has exhibited an output power of 15 W and the 8 mm of 28 W at Vds=25 V in pulsed conditions. The best power performance in continuous wave are 10.5 W and 15 W for 4 mm and 8 mm, respectively. Better than 20% PAE over the 2-6 GHz frequency range is achieved in CW.