[R-390] Re: Slighty OT: Question about tantalum caps (Barry)

[David Wise]

Depends on how much you ask from your caps.  Compared to aluminum, tantalums

(a) are more stable in value
(b) are less leaky
(c) have lower ESR
(d) have lower dissipation factor

(C) is less true than it used to be, with the development of
low-ESR aluminums, but in resonant or timing circuits that need
a big cap, if there isn't room for film, tantalum still rules.

> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Ed & Mary Wambold
> Sent: Wednesday, September 24, 2008 2:15 PM
> To: r-390 at mailman.qth.net
> Subject: [R-390] Re: Slighty OT: Question about tantalum caps (Barry)
>
>
> Barry,
>
> 47 mf @ 50v is 47 mf @ 50v, it does matter what type of cap
> you use, unless
> you are concerned about physical size. Tantalums are more
> compact and other
> than that, they are equivalent to regular electrolytics...
>
> Ed, N3LHB
>
> > Message: 2
> > Date: Tue, 23 Sep 2008 20:36:38 -0500
> > From: "Barry" <n4buq at knology.net>
> > Subject: [R-390] Slighty OT: Question about tantalum caps
> > To: "R390" <r-390 at mailman.qth.net>
> > Message-ID: <000601c91de5$fdbe4030$6401a8c0 at ingrnet.com>
> > Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> > reply-type=response
> >
> > I think I mentioned on this list that I'm in the process of
> thinking about
> > considering the possibility of maybe one day building a
> 9VDC power supply
> > for one of my radios.  Yes, it's solid state and begins
> with a "G" (and
> > ends
> > with "rundig") so if you want to stop reading here, I understand.
> >
> > I was getting the parts list together and the circuit calls
> for a few
> > miscellaneous caps, one being a 47uF 50V Solid Tantalum
> cap.  Perusing the
> > Mouser catalog, I find this capacitor is quite expensive
> (in excess of $20
> > each).
> >
> > Can anyone explain to me the advantage of using a solid
> tantalum over some
> > other "plain-jane" capacitor?  The circuit uses an LM317K and this
> > particular capacitor is connected across the output just before the
> > ammeter
> > and voltmeter.  (The circuit is in the 1978 ARRL Handbook
> (page 127)).
> >
> > I was fortunate to have meters that will make the project
> nice and figured
> > that would be lion's share of the cost, but this little cap
> (along with a
> > couple of other items) have really driven the cost of
> building this thing
> > nearly out of sight.
> >
> > Can someone/anyone tell me if another type of cap would
> work as well?  Are
> > the caps of today better than those of 30 years ago, so
> much so that maybe
> > the solid tantalum wouldn't be necessary?
> >
> > Thanks!
> >
> > Barry - N4BUQ
> >
> >
> >
>
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