What would an ideal Q2 be? Something like an FQP7P06 ?
Since I'll be moving 2.5 amps (30 watts) through it, I assume a heatsink of some sort would be a good idea? If the tab is in fact electrically isolated, I could just run an aluminum bar across the tabs.
It'll do the job. You could look for one with a lower on resistance and Id. It would be uncommon for the source or drain to not be connected to the tab.You're using the MOSFET as a switch. A typical FQP7P06 would have an Rds(on) of about 350m ohms at 2.5A. Power dissipation at 2.5A would be (2.5A)(2.5A)(350m ohms) = 2.2W. A heatsink is still needed.
I still find it odd the datasheet doesn't specify
You are right! The datasheet is missing that critical detail. The tab is almost always the same as the middle pin on any TO-220 package; they are presumably punched in one piece.Mind you, that datasheet is actually from 2001 (down near the bottom). That really is a rather poor device for your application, you would be much better off using a modern part requiring no heatsink. If it is a SMD part, just use these adapters:The chip plus the adapter will be no bigger than the TO-220 itself. You will have a vastly more compact assembly.
Searching "P-channel logic level FET" ...Well, this one would be an excellent choice but is in a "DPAK" format - small but somewhat easier than a SOT-23.This old one would appear to be adequate, not logic level but since you are going to drive it with at least 10 V, it should switch your 2.5 Amps easily with no heatsink.And it is in a TO-220 package.(By all means, someone can check my reading of the datasheets. )
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