GaAs MESFET performance

The operating frequency of RCA´s power GaAs MESFET amplifiers has been extended to 18 GHz. We have achieved 225 mW CW output power with 4.5 dB gain at 18 GHz from a 1200 µm source periphery device. At 15 GHz the same device yielded 451 mW output power with 5.2 dB gain with a power added efficiency of 12.5%. Under class B operating conditions we have achieved power added efficiencies as high as 68% at 4 GHz with a power output of 261 mW and a gain of 9.6 dB. The drain efficiency at this point was 77%. At 8 GHz, the highest power added efficiency achieved was 41.5% with 302 mW output power and 6.9 dB gain. A theoretical model has been formulated for the MESFET class B amplifiers. The calculated results are in good agreement with experimental data.