QFN-packaged highly-linear cascode GaN LNA MMIC from 0.5 to 3 GHz

A GaN high electron mobility transistor technology with a gate length of 0.25 μm has been used to design and fabricate a cascode broadband low noise amplifier (LNA). The two-stage monolithic microwave integrated circuit (MMIC) with feedback topology yields a bandwidth of 0.5-3 GHz at a constant gain of 35 dB and noise figures of less than 1.5 dB. A third order intercept point (OIP3) of up to 42.5 dBm was measured at 0.8 GHz, with a linear output power of 24 dBm over the full bandwidth. The MMIC was further assembled and measured in a low-cost plastic QFN package on an evaluation board with optimized thermal design and passive cooling. At a power dissipation of ~3 W the packaged LNA yields an OIP3 of 35-38 dBm over the full bandwidth at a noise figure of <; 1.9 dB.