The applications that MACOM cites include; a new generation of domestic and commercial microwave ovens in which a GaN-based PA replaces the magnetron; light-emitting-plasma-based lighting; automotive ignition; a range of drying and curing processes in industry and even domestically, with the ubiquitous laundry drying a possible market; medical applications such as tumour ablation (targeted delivery of heat), tissue warming, and sterilisation by heat.
Where RF energy has been generated by solid-state amplifiers, the prior technology has been LDMOS silicon: GaN has been seen, MACOM explains, as too expensive because it has been based on GaN on silicon carbide substrates. (GaN devices are invariably fabricated in an epitaxial layer of GaN grown on a carrier substrate: in earlier generation, SiC was technically easier. Silicon is much cheaper in that role, not least because larger wafer sizes are possible, allowing the normal learning curves of semiconductor production, moving to 150 mm then 200 mm wafers, to be applied.) MACOM has produced its current generation of parts not only using GaN-on-silicon, but moving to a moulded (plastic) package. There are four devices in this release, at 50, 100, 200 and 300W output; each offers gain of 17dB and efficiency of over 70%. The efficiency figure is a ‘true’ measure of DC-in to RF power out.
Using the 300W part, MACOM has also produced a PA module, a fully-assembled substrate of about 50 x 100 mm, for incorporation into a final product. In many cases – for example, manufacture of domestic microwave ovens for example – the appliance designers will have little experience of semiconductor amplifiers, or of routing RF power on PCBs: so a drop-in solution will be required. 300W out of a gain block with 17-dB added still requires significant drive, and MACOM has also produced an integrated module (above) with the complete RF path, and a digital control interface. The company expects to take these products, also, along a familiar electronics integration/shrink/cost reduction path.