Hi SK0480,
I personally have never used Darlingtons in parallel - the thought had never occurred to me. I don't see that it should pose any problems though if done right.
You are probably aware that when connecting BJTs in parallel, you need to use small current sharing resistors. One other very important thing that many people don't realise is that BJTs MUST be thermally coupled if used together (both in parallel or series), at minimum they should share the same heatsink but even better would be if they are part of the same IC. If this isn't observed, one of the two transistors will likely dominate and therefore pass most of the current, and so will get hotter, resulting in even more current flow etc. Long story short, it usually results in it going pop!
If you were to use the Darlingtons from the same IC, you would also have the advantages of Vbe's matching. It would be worth checking the specification sheet from the manufacturer of the IC, but I have seen a few different manufacturers stating "Outputs may be paralleled for higher current capabilities" (or something similar). The specifications might even give you an idea of how to go about connecting it all up.
Like I said, I have never tried this, but based on the theory I know, it should be OK. Perhaps the best thing to do would be to just try it (safely!) and see what happens!
I hope that helps. If there is anything else I can assist you with, please feel free to post.
Regards,
Oli
LabVIEW Student Ambassador
National Instruments UK
