RE: PWM stepper driver external bridge

sorry folks, attachment was deleted from my last post. If you are
interested, the cct for 1 of the 2 bridges required for each stepper drive
is available in the files area at:

http://www.egroups.com/files/CAD_CAM_EDM_DRO/stepdrv.jpg

the drive points are the two arrows on each side of the schematic and should
be driven rail to rail of the motor supply. Gate impedances have been
tailored to promote fast turn off and slower turnon. Loss of drive results
in all fets switching off. Fets are rated 100v but the bipolar transistors
(which must be the A versions) are rated max of 60v. Supply voltage could
probably be pushed to 45v without problems. Fets could be upgraded to the
540 series for higher current ratings, but the gate capacitance doubles and
may cause some problems if using high speed chopper ccts.

=======================================================
Lawrence Glaister VE7IT email: lg@...
1462 Madrona Drive http://jfm.bc.ca
Nanoose Bay BC Canada
V9P 9C9
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