High-power GaInP/GaAs HBTs with high breakdown voltage for X-band applications are presented. To demonstrate the capabilities of these devices, a simple monolithic amplifier is realized. For a single 12-finger device with 2/spl times/70 /spl mu/m/sup 2/ emitter finger size, an output power of 3.2 W at 9 GHz with 47% PAE is achieved.