At 08:24 AM 6/05/96 -0500, you wrote:
>The command station is currently using a power op-amp made by SGS Thomson,
>part L165.  It is only rated at 3A.  I will be switching to a full H bridge
>using discreet n-chan mosfets and a fet-driver to get more current.  The
>power op-amp might be a good approach for the decoder.  The disadvantage for
>a command station is it needs a bipolar supply.  The decoder inherently has
>a bipolar supply from the rails.  The only package information I have is a
>TO-220 style case.  There may be a surface mount power op-amp out there
>somewhere.  It's easy to get the op-amp to do bipolar but a little harder to
>do PWM.  I haven't thought about how to make it do PWM, but it shouldn't be
>too hard.

As you mentioned, power op amps need a bipolar supply which is a pain. Besides,
you aren't using the linear part. Single chip H bridges are easily available
 which
make using discrete solutions unecessary. I don't know about the cost factor
 though.
For example, the SGS Thomson L298 should give you enough juice. I don't remember
the rating but should be around 4A. It costs about AU$25. I remember seeing it
being used in a DCC station circuit and can dig it out for you if you like. For
low power applications I use a L293 rated at 600ma/1A. You get two in a 16/20
 pin
DIP. I've used it to drive a stepper off a PC parallel port.

Regards

Prashant
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