Under class-C common-base configuration, unit-finger InGaP/GaAs HBTs exhibit record power density of 15 mW/mu m(2) emitter area. However, the power density decreases rapidly with increasing number of emitter fingers. Based on measured dynamic drive and load lines under nearly isothermal pulse operations, it was concluded that the power density of multi-finger HBTs is limited by base-emitter reverse breakdown. In addition, the base-emitter breakdown voltage is much lower under RF operation than under DC operation. The RF base-emitter breakdown effect was added to a commercially available large-signal HBT model, which more accurately predicted the class-C power performance of common-base multi-finger HBTs. (c) 2007 Elsevier Ltd. All rights reserved.