BJT recommendation?

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Well, they're right under your nose. The 2N2219A and the 2N2905A are the same chips as the 2N2222A and 2N2907A, but they're in a TO-5 can and can dissipate something like 800mW. Sounds just right to me.

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If you're willing to use Pro Electron Euro parts, the BD135 and BD136 or other numbers in the same series will do the trick. They're TO-126, a bit smaller than TO-220. With a clip-on heatsink, or screwed to the board, they'll handle several watts. I got some of these from Futurlec for 20 cents apiece. If you do consider the TO-5 transistors, you'll have to pay more for the all metal case, probably double what the TO-126 cases cost. If you want anything more than a few hundred milliwatts, forget about using a TO-92.

I'd

Yeah, I did that before. Worked for me. But I've never seen any schematic anywhere that used that technique.

"Watson A.Name - "Watt Sun, the Dark Remover"" wrote in message news: snipped-for-privacy@corp.supernews.com...

I'd be hesitant to pump 700mW through a device rated for only 800mW, in a closed airspace. Those ratings are based on 25C ambient right next to the device; in closed airspace, the air heats up, and you have to derate. I'd feel more comfortable with something rated at least 1W.

Package looks perfect! It looks like min hfe is kind of low, but typical hfe is decent; I might have to hand-screen, which would be a pain. Mouser shows "non-stocked item"; Digikey doesn't list them. Nonetheless, I'll do a bit of hunting for them; they might do the trick. Thanks.

Our stock design uses the TIP29-TIP30 pair and we have had excellent results.

Jim

Hmmm. It looks to me as if Fairchild has a bunch of variants of these transistors, with part number suffixes which indicate the hfe binning.

Mouser has at least some versions (BD1361610STY, BD13616S and 16STU) in stock. The ones they don't have in stock seem to be the "6" suffix, which from the data sheet appears to be the lower-hfe versions.

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Ah - I saw those and assumed they were different transistors that started with the same couple of digits. Thanks! (You know what they say about "assume"...) hfe-binned variants is exactly what I need.

On a closer look at the datasheet, light dawns. I thought the "hfe classification" was telling me about statistical distribution (though the numbers did seem peculiar). I realize now it's part number suffix. Duh.

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As I mentioned, but you apparently overlooked and snipped it, they are available at

for 20 cents in 1 unit quantity. They come in three gain range classifiacations, -6, -10, and -16. So you don't have to do any selection whatsoever. Mouser carries Fairchild, and Fairchild makes them, so even if Mouser doesn't stock them you could order them. Also there is Fairchild Direct, which may be cheaper than Mouser.

35

The 2N2219A and 2N2905A are rated for 3W at 25 degrees case, derate at

20mW/~C. So you can run them at 1W with a small finned heatsink. Aavid makes some nice little heatsinks for TO-5s.

He complained that the BD135 and BD136 have too low gain, but the TIPs have even lower gain than they do.

What he didn't see apparently was that the BDs have gain ranges, so he can buy them with gains of 100 to 250, for example.

similar

"Watson A.Name - "Watt Sun, the Dark Remover"" wrote in message news: snipped-for-privacy@corp.supernews.com...

I did overlook it - sorry.

But as I mentioned, "I'd like to avoid heat sinks if possible because of the expense and assembly time." Maybe you overlooked that :-)

Anyway, the BD135/BD136, with hfe binning and easy availability now that I know how to look, are clearly the right answer, and I do appreciate the help!

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Again,. I think you snipped the part where I said to use a HS or the PC board.

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HTH.