They are marvels, and today's MOSFETs make for even smaller and lighter supplies. They bring noise with them though, so you will often see switching supplies th

They are marvels, and today's MOSFETs make for even smaller and lighter supplies. They bring noise with them though, so you will often see switching supplies that take line voltage down to some lower DC voltage, and then a crap ton of filters, connected to a linear supply that gives you the desired voltage in RF circuits.