Capacitor advice

Hi,
I'm making a circuit where 100n metal film capacitors are listed as
required.

This was the nearest I could find on my mail order site:
http://rswww.com/cgi-bin/bv/rswww/s...line&R=5373044&callingPage=/jsp/line/line.jsp

Does that component qualify as "metal film", or does it share broadly
the same characteristics as a metal film cap?

Thanks for helping.

 

Metal film means that the capacitor is made of metal and
plastic film. It is not very specific. Metalized film
means that the metal is vacuum deposited on the plastic film
and is very thin and compact, but may have fairly high
series resistance. Foil film capacitors are made with
layers of metal foil and film, stacked or wound around each
other. Since the foil is generally many times thicker than
the few atoms thickness in the metalized types, they have
lower series resistance and handle large peak currents better.

Then you have to ask about the kind of plastic the film is
made of. There are many choices and each has some
advantage. Cost, size, loss, temperature range, distortion
are some possibilities.

If the film type is not specified, the most common,
polyester (mylar) is probably good enough and small and cheap.

I might give more helpful advice if I knew the application.

 

"beatbox"

** Its a misprint.

Should be " metallised film ".



....... Phil

 

It *could* be metal fim. Rare I know.

More information is required.

Graahm

 

"Eeyore"

** Like these ones - fuckwit ?????????

http://www.radioshack.com/sm-1-f-250v-10-metal-film-capacitor--pi-2102515.html






......... Phil

 

We are in Usenet, not on www!!!

Yourself fuckwit!!!!



Best regards,

Daniel Mandic

 

Thanks all for the helpful info. Here is the circuit, for
clarification. It's a Midi -> CV converter. There are a few 100nF
capacitors in there.
http://m.bareille.free.fr/mcv628/MCV628A.PDF

 

"Daniel Mandic"

** Hey look - some hairy critter just poked its shit ugly head up out of a
dunny and puked !!

** Yeah - it.

ROTFL !!



....... Phil

 

Polyester / mylar film types will be just fine there. Very commonplace and very
inexpensive. Not special at all.

Graham

 

The capacitors you list would work for this application,
which is not at all critical. They are called supply bypass
capacitors, that provide a small local charge storage where
quick pulses of current may be needed without those pulses
having to race through the inductance of the supply
distribution lines.

More important is exactly where on the circuit board they
are mounted. They need to be connected between power supply
lines and ground, not in a cluster as shown, but at the
points where these supply lines connect to certain chips
being powered. For the +-15 volt lines, that would be right
at U6 and U8, and for the +5 line, right at U7.

It wouldn't hurt at all to add a pair between the +5 and +15
volt lines to ground at chips U3 and U4, too.

However, the voltage regulator, U2, may not be stable unless
C3 and C4 are very close to it.

If this project includes a printed circuit board, then these
locations are already taken care of, and all you have to do
is check that the capacitors you order have lead wire
spacings that fit the hole spacing of the board.

 

It does have a PCB. Thanks again!

 

---
Hardly. Every ceramic capacitor in the world is a metal film
capacitor, which type would be fine in the OP's application.

If the author of the schematic meant metalized film, then the error
was in not designating the caps "metalized film" or hyphenating
"metal film."

 

"John Fields"
Eeysore

** Dear John ....

The actual issue here is the industry accepted, unambiguous identifying type
name - as required for ordering purposes.

Try to follow the context.

Even when it is implied rather than visible.





...... Phil

 

There are also metalized glass capacitors, if your budget is big
enough, along with metalized Mica. One 25 KW UHF transmitter I worked
on used some very large open metalized mica capacitors that cost over
$900 in the '80s. It was at the output of the 250 watt driver stage.


Shove that up your #$%^&* UK donkey! ;-)


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

Dear Phil,

In the context that they're being used as supply bypass capacitors,
I believe it's much more likely that they're ceramic than metalized
plastic film, so the term 'metal film' is probably referring to the
sub-micron thick metal film "plates" sandwiched in between the
ceramic dielectric. An unusual usage for 'metal film', but stranger
things have happened, wouldn't you agree?

 

Whose hair?

Has it done good, yes? You rolled over my puke-dot.

But I got somehow in the right thread . Interesting.... Allthough, I
would suggest a real VC Analogue Sequencer. MIDI to CV are rightly
wrong, IMO.



Best Regards,

Daniel Mandic

 

I was referring to *film and foil* types as opposed to metallised film. They are
obviously noy needed here. I agree with your comment about the author of the
schematic btw.

Graham

 

Polyester film caps are widely used in European designed products for decoupling
actually. I gave up on ceramics after encountering a high failure rate when using
them (50V rating) on 17V supplies for decoupling.

Graham

 

"John Fields"
"Phil Allison"

** That is NOT the context.

YOU cannot invent context.






......... Phil

 

---
Yeah, that's kinda scary, especially when polyester caps are
self-healing.

What was it with the ceramics, a bad batch of caps or a really spiky
supply?