Re: BJT recommendation?

From: Watson A.Name - \ (NOSPAM_at_dslextreme.com)
Date: 03/25/05 

Date: Fri, 25 Mar 2005 03:03:25 -0800

"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:SrqdnX5zB8qhcd_fRVn-qw@speakeasy.net...
> "Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com>
wrote
> in message news:114535pd7eb7k50@corp.supernews.com...
> >
> > "Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
> > news:UN-dnVO829BQ99_fRVn-qQ@speakeasy.net...
> >> hfe around 100 - 300 [...] need to be able to dissipate 700mW
> >> continuously (inside a small chassis), without damage.
> >
> > 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.
>
> 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.
>
>
> > 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.
>
> 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.

As I mentioned, but you apparently overlooked and snipped it, they are
available at www.futurlec.com 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.
http://www.fairchild-direct.com/esales/SearchProducts.jsp?partNumber=BD1
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.