1-8-GHz GaN-based power amplifier using flip-chip bonding

We report the first gallium nitride (GaN)-based broad-band power amplifier, The circuit was fabricated on an AlN substrate using AlGaN/GaN power high-electron mobility transistors (HEMT's), grown on sapphire substrates, which were flip-chip bonded for thermal management. The amplifier employed a modified traveling-wave power amplifier (TWPA) topology that eliminated the backward wave of conventional TWPA's, Using four HEMT's each with 0.75-mu m gate length and 0.75-mm gate periphery, a small-signal gain of similar to 7 dB was obtained with a bandwidth of 1-8 GHz, At mid-band, an output power of 3.6 W was obtained when biased at V-ds, = 18 V and 4.5 W when biased at V-ds, = 22 V.