Abstract This paper presents the development of a 300W-class power amplifier (PA), a key component of a plasma source generation device that utilizes RF to generate plasma. To achieve this, a 150W-class GaN -based power amplifier device was designed and fabricated, which was then used to develop and verify the 300W-class power amplifier. The device was fabricated using Win Semiconductor's NP25 (0.25μm) semiconductor process. Performance evaluation using a dedicated test board confirmed its operation in the 2.4–2.5 GHz frequency band, achieving an output power of over 300W, an efficiency of 61%, and a gain of 13dB. The developed power amplifier can be utilized not only in the...