|
Look up your proposed part on Mouser's site, and click the "data sheet" link. Dive into that, and all will be revealed. A random choice showed that, based on power level selected, the un-heat-sinked (free-air) rating was derated to 20 to 60% of full rating. Only when mounted to a chassis was full rating achieved, and a specific surface area was required to do so. (Note that the percentages I mentioned are not "derated by 20% (so, 80%)" but rather derated TO 20%.)
Each mfg. probably has different stats, so pick one out and click the data sheet link.
Good luck!
Chip
|