Capacitor advice

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

** Like these ones - f****it ?????????

........ Phil

We are in Usenet, not on www!!!

Yourself f****it!!!!

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.

"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

(snip)

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."

** 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? :-)

--
JF

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

using

--
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?