A compact design for a 2.5 kW solid-state power amplifier (PA) based on 330-W laterally diffused metal–oxide semiconductor transistors over 1.2–1.4 GHz is proposed. The design procedure is started with the design and implementation of a 330-W unit amplifier (UA) independently. Optimum load and source impedances of the UA are obtained by pulling the source and load impedances with the aid of the simulator utility provided in Advanced Design System. The input–output matching networks are designed and implemented using multi-section microstrip transmission lines. In order to construct a 2.5-kW high PA (HPA), the eight pieces of designed UA are combined. A low-loss 1–8 way planar binary power divider with an 8–1 way planar binary power combiner is used to divide and combine the microwave signals through eight UAs. The HPA delivers 63.7–64.3 dBm output power with 16.7–17.3 dB power gain and 55–60.4% power-added efficiency over 1.2–1.4 GHz. To the best of the authors' knowledge, the most compact HPA design using packaged transistor at L-band with such high output power level ever reported is presented.