I remember building a PWM driver for my electric trains in the 70's.

I used a monster Ge (not Silicon!) Transistor as the pass element.
Once implemented, it was far better than the junk ones that came (series
resistor)
and better than what I did with Auto transformers driving the older
pacs.

It was smooth with the small dc motors of the N gauge trains pulling 20
or so cars
up a hill and around a corner. It would just never lug down.

I still have the unit somewhere in the shop - trains in the attic.

Martin
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder