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This paper presents a broadband gallium-arsenide pseudomorphic high-electron-mobilitytransistor (GaAs pHEMT) power amplifier integrated circuit (PAIC) based on a dual-frequency selective impedance matching technique for warfare applications. For a broadband PA design, lower and upper-frequency corners where serious performance degradation is likely to occur should be carefully considered. Feedback and resistive biasing circuits were adopted for driver and main stages to making their frequency responses as flat as possible. Optimum impedances of not only extended lower and upper-frequency corners but also center frequency, were then extracted. Such dual-frequency selective impedance matching technique was applied for extended lower and upper-frequency corners while checking the mismatch level for the center frequency. The proposed broadband PAIC for frequency band from 6 to 18 GHz was designed using a 0.15 μm GaAs enhanced-mode pHEMT (E-pHEMT) process. The implemented broadband PAIC with a simple two-stage structure had a very small chip size of 1.19×0.82 mm2. It exhibited a power gain of more than 16.4 dB and output power of 19.2 dBm. Very flat characteristics in power gain and an output power within ±1.0 dB through the whole band were achieved.