Tim Wescott
Guest
Wed Feb 01, 2012 6:50 am
I realized yesterday that gold electrolytics seem to have disappeared
from the market.
What do folks use when they need a really low-leakage capacitor?
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
Fred Bartoli
Guest
Wed Feb 01, 2012 11:59 am
Tim Wescott a écrit :
Quote:
I realized yesterday that gold electrolytics seem to have disappeared
from the market.
What do folks use when they need a really low-leakage capacitor?
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.
--
Thanks,
Fred.
John Larkin
Guest
Wed Feb 01, 2012 5:52 pm
On Tue, 31 Jan 2012 23:50:43 -0600, Tim Wescott <tim_at_seemywebsite.com>
wrote:
Quote:
I realized yesterday that gold electrolytics seem to have disappeared
from the market.
What do folks use when they need a really low-leakage capacitor?
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.
--
John Larkin, President Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
Tim Wescott
Guest
Thu Feb 02, 2012 10:32 pm
On Wed, 01 Feb 2012 08:52:39 -0800, John Larkin wrote:
Quote:
On Tue, 31 Jan 2012 23:50:43 -0600, Tim Wescott <tim_at_seemywebsite.com
wrote:
I realized yesterday that gold electrolytics seem to have disappeared
from the market.
What do folks use when they need a really low-leakage capacitor?
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.
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
John Devereux
Guest
Fri Feb 03, 2012 6:52 am
Tim Wescott <tim_at_seemywebsite.com> writes:
Quote:
On Wed, 01 Feb 2012 08:52:39 -0800, John Larkin wrote:
On Tue, 31 Jan 2012 23:50:43 -0600, Tim Wescott <tim_at_seemywebsite.com
wrote:
I realized yesterday that gold electrolytics seem to have disappeared
from the market.
What do folks use when they need a really low-leakage capacitor?
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.
--
John Devereux
Tim Wescott
Guest
Fri Feb 03, 2012 7:57 am
On Fri, 03 Feb 2012 05:52:20 +0000, John Devereux wrote:
Quote:
Tim Wescott <tim_at_seemywebsite.com> writes:
On Wed, 01 Feb 2012 08:52:39 -0800, John Larkin wrote:
On Tue, 31 Jan 2012 23:50:43 -0600, Tim Wescott <tim_at_seemywebsite.com
wrote:
I realized yesterday that gold electrolytics seem to have disappeared
from the market.
What do folks use when they need a really low-leakage capacitor?
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...
--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
John Devereux
Guest
Fri Feb 03, 2012 12:55 pm
Tim Wescott <tim_at_seemywebsite.please> writes:
Quote:
On Fri, 03 Feb 2012 05:52:20 +0000, John Devereux wrote:
Tim Wescott <tim_at_seemywebsite.com> writes:
On Wed, 01 Feb 2012 08:52:39 -0800, John Larkin wrote:
On Tue, 31 Jan 2012 23:50:43 -0600, Tim Wescott <tim_at_seemywebsite.com
wrote:
I realized yesterday that gold electrolytics seem to have disappeared
from the market.
What do folks use when they need a really low-leakage capacitor?
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...
--
John Devereux
Spehro Pefhany
Guest
Fri Feb 03, 2012 2:00 pm
On Tue, 31 Jan 2012 23:50:43 -0600, the renowned Tim Wescott
<tim_at_seemywebsite.com> wrote:
Quote:
I realized yesterday that gold electrolytics seem to have disappeared
from the market.
What do folks use when they need a really low-leakage capacitor?
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
--
"it's the network..." "The Journey is the reward"
speff_at_interlog.com Info for manufacturers:
http://www.trexon.com
Embedded software/hardware/analog Info for designers:
http://www.speff.com
Archimedes' Lever
Guest
Fri Feb 03, 2012 2:38 pm
On Fri, 03 Feb 2012 08:00:31 -0500, Spehro Pefhany
<speffSNIP_at_interlogDOTyou.knowwhat> wrote:
Quote:
On Tue, 31 Jan 2012 23:50:43 -0600, the renowned Tim Wescott
tim_at_seemywebsite.com> wrote:
I realized yesterday that gold electrolytics seem to have disappeared
from the market.
What do folks use when they need a really low-leakage capacitor?
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.
Tim Wescott
Guest
Fri Feb 03, 2012 6:43 pm
On Fri, 03 Feb 2012 05:38:55 -0800, Archimedes' Lever wrote:
Quote:
On Fri, 03 Feb 2012 08:00:31 -0500, Spehro Pefhany
speffSNIP_at_interlogDOTyou.knowwhat> wrote:
On Tue, 31 Jan 2012 23:50:43 -0600, the renowned Tim Wescott
tim_at_seemywebsite.com> wrote:
I realized yesterday that gold electrolytics seem to have disappeared
from the market.
What do folks use when they need a really low-leakage capacitor?
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).
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
