Question re: about current control schematic

An article about current control in steppers by Suded Emanuel at:

http://www.eio.com/crntctrl.htm

has a schematic. When I asked on the Nuts and Volts Forum about using
a mosfet instead of the Darlington, I got this reply:

"Wow, that schematic appears to have multiple errors. At least two at
first glance. It looks like they are trying to do a classic buck
regulator. The base of the BDW84 is grounded, which means the PWM chip
can't do anything to affect it. D1 should be grounded, but not the
transistor base. Also, looks like the BDW84 is in backwards (collector
and emitter reversed). So, be aware of that in any case."

I don't know enough about electronics to know if this is true. Any
comment from the electronically unimpaired appreciated.

Grant Fair