Power Electronics Building Blocks and potential power modulator applications Power Electronic Building Blocks (PEBBs) are power processors. A PEBB is not a specific semiconductor material, not a device, nor a circuit topology. It is the search for the common electrical, mechanical and thermal denominators of all these, allowing integration of all these technologies. It is not; “one size fits all”. There will be several blocks that will fit together to perform the majority of everydaypower electronic jobs. Like a set of children’s interlocking blocks, PEBBs will be a rational and simple set of blocks and procedures that most any designer or architect can use to build electrical systems. The Office of Naval Research (ONR) is developing Power Electronic Building Blocks to achieve: increased power density, “user friendly” design (“plug and play” power modules), and multi-functionality. Digital controls, integrated with higher frequency and more robust power circuits, enable modular powersystems with lower size, weight, and cost-while increasing performance. Although the day when solid-state will replace tubes in high-power modulator applications is still in the future, many near-term opportunities exist for PEBBs and associated technologies. This paper presents requirements, opportunities and issues for standardized power modules. First, an overview of the PEBB program is given. Then, opportunities are examined for technologies developed by the PEBB program