28 Nov
2010
28 Nov
'10
8:16 p.m.
Though the Motorola appnote Al linked to explains that
you can do the
same thing with a constant-current source, DFF and a pair of switching
transistors. I suspect "fast" is the order of the day for the
transistors, which probably means the BC547 and BC847 aren't suitable.
I don;t think the transistors used were that exotic. Things like 2N3904s,
for example.
The semi-0discrete solution ('74 as a divide by 2 and a handful of
transistors) turns up all over the place. It's easy to design and reliable.
There were combined read/write chips (I can try to find some details),
but they are very few and fr between.
Although whether I've got enough clearance to
shove a PDIP chip in there
without fouling the drive belt or flywheel is another question entirely...
Do you have to pack it into the same volume as the original drive?
-tony