High-efficiency GaN power amplifier on Si substrate supports development of mobile communications base stations

June 22, 2012 // By Paul Buckley
Mitsubishi Electric Corporation has developed a prototype high-output, high-efficiency 2 GHz power amplifier for mobile communications base stations.

The amplifier, which features a gallium nitride (GaN) transistor on a silicon (Si) substrate instead of a more costly silicon carbide (SiC), achieves a conversion efficiency rating of 70%, unprecedented among 2 GHz power amplifiers with outputs of 150 W or higher.

The amplifier will help the development of smaller and more power-efficient base station transmitters. The installation of such equipment in tighter spaces will help expand wireless network coverage to accommodate increasing wireless traffic due to smartphone proliferation.

While amplifiers that use GaN transistors consume less power and have a higher output than amplifiers made with silicon transistors, they typically require a more robust substrate made of silicon carbide, which elevates the cost. Initial efforts to develop a GaN transistor using a Si substrate were hampered by deformation between the GaN layer and Si substrate, which led to increased loss and decreased power conversion efficiency. Eventually, however, the company designed a high-performance transistor by optimizing the GaN crystal structure and inserting a buffer layer between the GaN layer and Si substrate.

Mitsubishi Electric’s new GaN power amplifier made with affordable silicon substrate achieves a power conversion efficiency of 70% at 2.1 GHz, largely improving upon the 58% conversion efficiency of Si transistor amplifiers currently available commercially.

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