Question about Capacitors

K2LRV wrote in news:225bd33d-09e4-40fe-9ae2- snipped-for-privacy@t54g2000hsg.googlegroups.com:

There are lots of guidelines, but capacitors are very complicated. The simplest approach is to use what's worked, so think about what you want to do, find a board from a successful commercial device that uses the same kind of functions you want to make, and use the capacitors they do. To do that you'll have to reverse engineer the circuit thoroughly or get a circuit diagram from the maker.

For specifics, as I know them (limited knowledge though) try these:

Tantalum for long life and stability, decoupling close to chips and other sensitive parts, and limit inrush current if you want to be sure they don't fail early. Electrolytic for large values, cheap, where reliability isn't critical, and no harm is done if they burst. (Sealed, cheap boxes, basically). Ceramic. Variable specs, but the really low values usually have better dielectrics than larger values, but avoid using them for critical timing functions. People do use them for timing things, but best not to. Metallised polyester, mylar, polypropylene, and many other rare ones are good for timing, have low variance with temperature and humidity, generally good for accurate timers. Teflon, polystyrene, and other high-cost caps, good for radio frequency timing, very accurate values and stability in a wide range of conditions. Mylar, teflon, polypropylene and oil-filled types for high voltage.

There is so much to add to this, and probably some corrections. Maybe the only really good way to know is to look at any circuit that is common, OLD, and still working well, trusted by lots of people. See how they did it.

It depends. Here's a brief starting point

Lostgallifreyan wrote in news:Xns9B3EA2831BE81zoodlewurdle@216.196.109.145:

By 'old' I mean about ten years. No point in looking much further back that that in most cases. Also look at new types that make use of better materials that were known before but not cheap to exploit. New tantalums are good, and most polymer dielectrics are improvements of old ideas. Probably true for ceramics too.

I think there's also a section on the subject in Bob Pease's _Troubleshooting analog circuits_.

Don't use ceramic with high ripple currents, if you want them to be quiet. They can act like tiny piezo buzzers. I used a big electrolytic with a smaller tantalum in that case, no noise at all.

Oh God !

Buy a book !

Graham

If you need to troubleshoot a decent capacitor you probably aren't living in the real world.

Correction. There's no 'probably' about it.

Graham

Ceramics are NEVER used with high ripple currents you brain dead defective.

Go away and die.

Graham

Wow, someone's off his meds again.

Oh really..

Tell that to the military customers that required us to test the ripple currents on ceramic caps back when I was at Semco. We didn't actually make the ceramic material there how ever, we did complete the rest of the cap's structure.

The main line was mica epoxy dips with very high Q.

Think before you speak!, not every one makes only audio circuits.

As a first step, "electrolytic" usually means "aluminium electrolytic", and "tantalum" means "tantalum electrolytic". Both types of electrolytic capacitor have much larger capacitance than a similar size non-electrolytic, so will be used where a large value capacitance is required.

Provide an example of a ceramic caps with high ripple current before talking out of your arse.

Graham

Mica caps with very high ripple currents ?

Bwahahahahahahahahahhahah

That would go against my original recommendation.

That is, providing an example of ceramics used in a high-ripple-current situation would go against my original recommendation.

Is that the real Graham Stevenson or a forgery ? The Path: looks genuine to me.

You absolutely do not know what you're talking about..

Stop embarrassing your self and move to a different subject.

By Eye-Sore.

Please post ripple current ratings for mica caps.

I look forward to seeing one that can handle say 10A !

MORON

Graham

It's genuine.

Anyone who thinks you use ceramic caps as reservoir caps needs their brain examined.

Graham