This talk will present power amplifier design considerations for efficient, high-power phased arrays. Beyond the typical power amplifier goals of output power, bandwidth and efficiency, we will consider other array-specific features, such as the ability to dynamically measure the antenna load impedance (which typically varies due to scan angle), and will discuss analog- vs digital-domain considerations for distortion reduction techniques in a system with large numbers of active elements. The work will focus on the perspective of GaN and GaAs MMIC design, and the associated capabilities and limitations.