We present an initial demonstration of GaN-based broad-band power amplifiers in the form of a flip-chip integrated circuit (FC-IC) with AlN as the circuit substrates. The input matching consists of a high-to-low impedance transformer and an L-C-R broad-band network. Using 0.7-m gate-length GaN high-electron-mobility transistors (HEMT's) with current-gain and power-gain cutoff frequencies of 18 and 35 GHz, excellent transducer gain up to 11.5 dB at 8 GHz, along with a bandwidth of 3-9 GHz, was

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... hieved. The saturation power levels were about 32 and 35 dBm, respectively, for these two amplifiers using 1-and 2-mm-wide devices, which are about twice as high as achievable with GaAs-based counterparts of the same sizes. Index Terms-Amplifier, field-effect transistors, gallium-nitride (GaN), microwave power.