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[Amps] Bias Zener Diodes In Parallel ?

To: <amps@contesting.com>
Subject: [Amps] Bias Zener Diodes In Parallel ?
From: stevek@jmr.com (Steve Katz)
Date: Thu, 18 Jul 2002 15:48:19 -0700
> How about the old trick of putting a power resistor in parallel with the
> zener to take some of the "heat."
> 
> WA5JCI  
> 
> //I wouldn't do that; it makes for a pretty sloppy regulator, having no
> real "knee."  I don't understand why hams resist simply using components
> designed for the task at hand -- am I missing something?  I can buy DO-5
> case, 50W, 100Apk Iz rated, 5% tolerance zeners all day long for less than
> the cost of a six-pack of 807's.  And just one will do the job, and likely
> outlast the operator.
> 
> -WB2WIK/6
> 
> 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
> > > >_______________________________________________
> > > >Amps mailing list
> > > >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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