This work deals with the analysis, design, and realization of AlGaN/GaN power amplifier monolithic microwave integrated circuits (MMICs) at K/Ka-band between 20 GHz and 30 GHz. Three different European AlGaN/GaN technologies are evaluated and compared. Furthermore, technological limits in terms of output power, efficiency, and chip size with respect to the application in distributed antenna systems are extracted. As a result, state-of-the-art performance is demonstrated for the manufactured MMICs.