Where'd they go? (Gold electrolytics)

Tim Wescott a écrit :

I tend to use film caps when possible. Then tantalums (Joerg would say that when they leak you have a big sonic alarm). You can also use 2 electrolytics in series and bias the middle point with a high value resistor so that the cap on the side you want no leakage has no voltage across it.

Polymer aluminum caps are pretty good. Unlike wet caps, leakage is low and doesn't change much with voltage, right up to when they punch through and short.

Tantalums are pretty good.

But ceramics are available in 10's of uFs, too.

I was looking at the specifications for polymer aluminum electrolytics, and the specified leakage current wasn't any better than the specified leakage of a plain ol' aluminum electrolytic. Both my customer and I are a bit paranoid about counting on circuit elements beyond their rated parameters, so something that's rated to be low leakage would be a cool thing.

Some of the supercapacitors are touted as "low leakage" but I don't know how they compare with other types.

Astonishingly high prices.

A lithium coin cell costs as much as a few second's worth of capacitors...

Yes I have never seen the point of them either...

Generally, when I need a high value low leakage capacitor, I'll use a low-leakage aluminum electrolytic. Just because "gold" (wasn't that just Panasonic's trade name) caps have disappeared from Digikey doesn't mean they're generically gone. Many, if not most, of the e-cap makers catalog low leakage parts- but they are not necessarily stocked on this side of the Pacific.

Mouser still stocks Nichicon low leakage e-caps, but you can get them in bulk from many GCA factories.

Best regards, Spehro Pefhany

You are correct. There never was a "gold" EL, as in some variant of what the industry originally engineered which used Gold. It was a trade name that was apparently quite successful. They got the Gold.

What they sold was a technology they discovered and patented (and branded), which gave the yields he desires, but actual "Gold" in the caps would have made them considerably more expensive and I do not recall them being $10 or $20 each. So it was just a damn good name.

But *that* may well be exactly what he is referring to, as he did not remove that vaguery from the query.

Hmm. I assumed that they were, indeed, using gold in the chemistry. IIRC the price would have been consistent with using a thin flash of gold on aluminum foil or plastic film.

But, if it was just super-low-leakage aluminum caps, that's fine (assuming I can find them).