I have a small project to make where I need to provide DC isolation for
a low impedence audio circuit. I need a non-polarized capacitor of about
100 uf. Failing this, what would be the impact of two 220 uf polarized
electrolytic capacitors in series? The latter would be more easily
obtained. This is a one time project so buying parts in bulk is not an
option.

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P

**THE-RFI-EMI-GUY** wrote:

I have a small project to make where I need to provide DC isolation for
a low impedence audio circuit. I need a non-polarized capacitor of about
100 uf. Failing this, what would be the impact of two 220 uf polarized
electrolytic capacitors in series? The latter would be more easily
obtained. This is a one time project so buying parts in bulk is not an
option.

i've seen many used like that with an encapsulated
package to make it look like a single.
btw.
i could be wrong here but if your looking for
100 uf then i think you should keep with using
2 100 uf in series because one is going to short
while the other charges and they need to be back to
back of course.


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

"Jamie" t wrote in message
...
**THE-RFI-EMI-GUY** wrote:

I have a small project to make where I need to provide DC isolation for a
low impedence audio circuit. I need a non-polarized capacitor of about
100 uf. Failing this, what would be the impact of two 220 uf polarized
electrolytic capacitors in series? The latter would be more easily
obtained. This is a one time project so buying parts in bulk is not an
option.

i've seen many used like that with an encapsulated
package to make it look like a single.
btw.
i could be wrong here but if your looking for
100 uf then i think you should keep with using
2 100 uf in series because one is going to short
while the other charges and they need to be back to
back of course.


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5


A clamping diode in parallel with each capacitor wouldn't hurt, just to make
sure reverse charging can't happen!

"ian field" wrote in message
...

"Jamie" t wrote in
message ...
**THE-RFI-EMI-GUY** wrote:

I have a small project to make where I need to provide DC isolation for
a low impedence audio circuit. I need a non-polarized capacitor of about
100 uf. Failing this, what would be the impact of two 220 uf polarized
electrolytic capacitors in series? The latter would be more easily
obtained. This is a one time project so buying parts in bulk is not an
option.

i've seen many used like that with an encapsulated
package to make it look like a single.
btw.
i could be wrong here but if your looking for
100 uf then i think you should keep with using
2 100 uf in series because one is going to short
while the other charges and they need to be back to
back of course.


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5


A clamping diode in parallel with each capacitor wouldn't hurt, just to
make sure reverse charging can't happen!

In order to get 100uF with two caps in series, they will each need to be 200
( 220 ) uF. I have seen this done many times to produce a bipolar
electrolytic. Usually, it's the two " - " terminals that are joined, leaving
the two " + " terminals for connection. I don't know whether there's some
valid reason for this. I seem to remember reading in the dim distant past,
that it's something to do with which is the outer foil in the cap, but I
don't really see why this should make any difference, and I'm sure it won't
in an audio coupling application. 'Genuine' bipolars are readily available
in this sort of value.

Arfa

"Arfa Daily" wrote in message
...

"ian field" wrote in message
...

"Jamie" t wrote in
message ...
**THE-RFI-EMI-GUY** wrote:

I have a small project to make where I need to provide DC isolation for
a low impedence audio circuit. I need a non-polarized capacitor of
about 100 uf. Failing this, what would be the impact of two 220 uf
polarized electrolytic capacitors in series? The latter would be more
easily obtained. This is a one time project so buying parts in bulk is
not an option.

i've seen many used like that with an encapsulated
package to make it look like a single.
btw.
i could be wrong here but if your looking for
100 uf then i think you should keep with using
2 100 uf in series because one is going to short
while the other charges and they need to be back to
back of course.


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5


A clamping diode in parallel with each capacitor wouldn't hurt, just to
make sure reverse charging can't happen!

In order to get 100uF with two caps in series, they will each need to be
200 ( 220 ) uF. I have seen this done many times to produce a bipolar
electrolytic. Usually, it's the two " - " terminals that are joined,
leaving the two " + " terminals for connection. I don't know whether
there's some valid reason for this. I seem to remember reading in the dim
distant past, that it's something to do with which is the outer foil in
the cap, but I don't really see why this should make any difference, and
I'm sure it won't in an audio coupling application. 'Genuine' bipolars are
readily available in this sort of value.

Arfa


In my experience non-polar electrolytics have tended to be unreliable,
expensive & oversized!

"ian field" wrote in message
...

"Arfa Daily" wrote in message
...

"ian field" wrote in message
...

"Jamie" t wrote in
message ...
**THE-RFI-EMI-GUY** wrote:

I have a small project to make where I need to provide DC isolation
for a low impedence audio circuit. I need a non-polarized capacitor of
about 100 uf. Failing this, what would be the impact of two 220 uf
polarized electrolytic capacitors in series? The latter would be more
easily obtained. This is a one time project so buying parts in bulk is
not an option.

i've seen many used like that with an encapsulated
package to make it look like a single.
btw.
i could be wrong here but if your looking for
100 uf then i think you should keep with using
2 100 uf in series because one is going to short
while the other charges and they need to be back to
back of course.


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5


A clamping diode in parallel with each capacitor wouldn't hurt, just to
make sure reverse charging can't happen!

In order to get 100uF with two caps in series, they will each need to be
200 ( 220 ) uF. I have seen this done many times to produce a bipolar
electrolytic. Usually, it's the two " - " terminals that are joined,
leaving the two " + " terminals for connection. I don't know whether
there's some valid reason for this. I seem to remember reading in the dim
distant past, that it's something to do with which is the outer foil in
the cap, but I don't really see why this should make any difference, and
I'm sure it won't in an audio coupling application. 'Genuine' bipolars
are readily available in this sort of value.

Arfa


In my experience non-polar electrolytics have tended to be unreliable,
expensive & oversized!

Hi Ian
Yeah, interesting you should say that. They do tend to be bigger, although
I'm not sure that I've really found them any less reliable. Even given that
they are bigger, I guess that one of them has still got to take up less
board space than two regulars back to back, though.

Arfa