How about the old trick of putting a power resistor in parallel with the
zener to take some of the "heat."
WA5JCI
Steve Katz wrote:
>
> I should add to my previous comment re DO-5 and outline drawings...
>
> A 5W "air cooled" diode usually isn't really air cooled. It's cooled by its
> leads, in most cases; thus, the Rthj-a is not the formula used for
> calculating junction temperature, but rather Rthj-L, where "L" is the lead.
>
> -WB2WIK/6
>
> "If everything seems under control, you're just not going fast enough." -
> Mario Andretti
>
> > -----Original Message-----
> > From: 2 [SMTP:2@vc.net]
> > Sent: Thursday, July 18, 2002 2:07 PM
> > To: Steve Katz; W8JI@contesting.com; AMPS; Douglas R Snowden
> > Subject: RE: [Amps] Bias Zener Diodes In Parallel ?
> >
> > In the Digikey catalog, 5w zeners are axial-lead air-cooled devices.
> >
> > >
> > >
> > >
> > >
> > >> > [Steve Katz] Hi Rich. Case temp of a DO-5 stud,
> > >>
> > >> I have never seen anything smaller than 10w in a stud mount. 3A axial
> > >> lead rectifiers are in a DO-5 case.
> > >>
> > > ??? Not sure what you mean, here. The DO-5 zener devices I use are
> > >normally rated 50W at 55 degrees (C) Tc. Readily available from many
> > >sources for a few dollars. The advantage is their high peak current
> > rating,
> > >usually hundreds of Amperes for a low-value Vz. 3A axial lead rectifiers
> > >aren't DO-5, they're usually DO-2, DO-41, DO-42, etc.
> > >
> > > -Steve WB2WIK/6
> > >
> > >
> > >
> > >> - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
> > >> www.vcnet.com/measures.
> > >> end
> > >_______________________________________________
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> > >Amps@contesting.com
> > >http://lists.contesting.com/mailman/listinfo/amps
> > >
> >
> >
> > - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
> > www.vcnet.com/measures.
> > end
> >
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