Comment by adrian_b
3 days ago
Now there are gallium nitride microwave transistors that can produce very high microwave power at very high efficiency. So that is no longer a limitation.
Microwave ovens with such transistors have been demonstrated, which have the advantage of modulating the microwaves in such a way as to achieve a more uniform heating throughout the oven, than can be achieved with the fixed-frequency magnetrons.
At least for now, such microwave ovens with transistors might be encountered only in some professional applications, because these transistors together with the associated control circuits remain much more expensive than magnetrons.
They would be ridiculously expensive compared to a cavity magnetron and have no real advantage though.
They are ridiculously expensive, but there was an article in a magazine that said that a certain vendor of ready-to-eat food uses for cooking its food an industrial microwave oven with gallium nitride transistors instead of a magnetron.
Like I have said, the advantage of transistors is that it is easy to modulate in frequency the microwaves. This avoids to have standing waves inside the oven, which cause cold spots and hot spots, so they ensure that heating is uniform everywhere in the oven.
I assume that this advantage is more important for a big industrial oven, where many portions of food are cooked simultaneously and it is desired that all of them are cooked uniformly.
But for home users, magnetrons will not be replaced any time soon.