TO-3 (TO-204AA) MOSFET Packages

Thread Starter

Robin Mitchell

Joined Oct 25, 2009
Hi all,

So today in my million boxes of IC tubes I came across a tube of 11 x IRF450 MOSFETs. Now I was about to use 4 in a project until I googled the parts. Apparently they cost up to £40 a piece :eek:! No way am I going to use 4 on a pet project. Here is a picture of the package:

I need these packages because of their fantastic ability to dissipate heat. So my question is this : Are there any cheap transistors in similar packages that can dissipate large amounts of power (say 10W to 100W)? If not, what packages would you guys and gals suggest for such power ratings?

All the best,


Joined Aug 1, 2013
In my experience, the TO-3 package is a pain to use and not nearly as thermally efficient as later plastic packages. A TO-247 moves a lot more heat with a single mounting hole. Note that the heat source in a TO-3 is just off to the side of the pins, an area that does not make great contact with the heatsink because of the holes required for the pins.

And, so what if their value is high. You didn't pay 40 pounds apiece, so their value to you is whatever you paid. You have them, you're not committing a production product to a long-term cost, there is nothing on the horizon for which they would be uniquely qualified, etc. If it were me, I'd be glad I had such excellent parts cheap and use them.