Polystyrene capacitors for filter networks?

P

Paul Burridge

Guest
Hi,

They look worryingly inductive on visual inspection (there are metal
foils rolled up in thar by the look of it.) And yet the CPC catalogue
says that their properties make them ideal for use in filters. Has
anyone any remarks (favourable or otherwise) to make about the use of
this type of cap in filter apps?

p.
--

The BBC: Licensed at public expense to spread lies.
 
Hi Paul!

There are non-inductively wound ones specifically for the purpose. The
mfr. specs should show an ESR curve - the non-inductive ones are pretty
flat to their SRF.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca
 
"Paul Burridge" <pb@osiris1.notthisbit.co.uk> wrote in message
news:6afg50lhac3arueiodioejthtojlr3tten@4ax.com...
Hi,

They look worryingly inductive on visual inspection (there are metal
foils rolled up in thar by the look of it.) And yet the CPC catalogue
says that their properties make them ideal for use in filters. Has
anyone any remarks (favourable or otherwise) to make about the use of
this type of cap in filter apps?
Click to expand...
They are OK for LF filters, the inductance won't make any appreciable
difference and they are available with 1% tolerance. They are getting
difficult to find. They are also useful for RF oscillators.

Leon
 
"Paul Burridge" <pb@osiris1.notthisbit.co.uk> wrote in message
news:6afg50lhac3arueiodioejthtojlr3tten@4ax.com...
| Hi,
|
| They look worryingly inductive on visual inspection (there are metal
| foils rolled up in thar by the look of it.) And yet the CPC catalogue
| says that their properties make them ideal for use in filters. Has
| anyone any remarks (favourable or otherwise) to make about the use of
| this type of cap in filter apps?
|
| p.
| --
|
| The BBC: Licensed at public expense to spread lies.

Silly boy...... Go and find out about construction methods. The
metallisation is offset so the end terminations parallel the internal
layers.

DNA
 
On Wed, 17 Mar 2004 15:45:34 -0000, the renowned "Emoneg"
<Emoneg@nothere.com> wrote:

"Paul Burridge" <pb@osiris1.notthisbit.co.uk> wrote in message
news:6afg50lhac3arueiodioejthtojlr3tten@4ax.com...
| Hi,
|
| They look worryingly inductive on visual inspection (there are metal
| foils rolled up in thar by the look of it.) And yet the CPC catalogue
| says that their properties make them ideal for use in filters. Has
| anyone any remarks (favourable or otherwise) to make about the use of
| this type of cap in filter apps?
|
| p.
| --
|
| The BBC: Licensed at public expense to spread lies.

Silly boy...... Go and find out about construction methods. The
metallisation is offset so the end terminations parallel the internal
layers.

DNA
Click to expand...
Yup. Take two sheets of letter-size (okay, A4) paper and lay one on
top of the other but the top one to the right by 1/2". These are like
the plates of your capacitor. Now roll them up from the bottom to the
top into a tight roll. Imagine you connect to all the right end (in
parallel) by dipping it in some conductive goop, and call that lead A.
Do the same to the left, and call it lead B. The coiled construction
adds no inductance.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
Yeah, they're rolled up, but the contact is made across the ends,
generally, not just at one location in the roll. (That's why you
should build that vector network analyzer...) But I'd avoid them:
they can't take the heat. C0G ceramics and polyprops are both good.
C0G ceramics are available up to 10nF or so even in SMT; polyprops
down to 1nF at least and up to many uF.

Cheers,
Tom

Paul Burridge <pb@osiris1.notthisbit.co.uk> wrote in message news:<6afg50lhac3arueiodioejthtojlr3tten@4ax.com>...
Hi,

They look worryingly inductive on visual inspection (there are metal
foils rolled up in thar by the look of it.) And yet the CPC catalogue
says that their properties make them ideal for use in filters. Has
anyone any remarks (favourable or otherwise) to make about the use of
this type of cap in filter apps?

p.
Click to expand...
 
On 17 Mar 2004 10:12:04 -0800, the renowned k7itm@aol.com (Tom Bruhns)
wrote:

Yeah, they're rolled up, but the contact is made across the ends,
generally, not just at one location in the roll. (That's why you
should build that vector network analyzer...) But I'd avoid them:
they can't take the heat. C0G ceramics and polyprops are both good.
C0G ceramics are available up to 10nF or so even in SMT; polyprops
down to 1nF at least and up to many uF.
Click to expand...
Would you believe 100nF/25V C0G in 1206? Not insanely expensive
either.

http://www.murata.com/catalog/c02/es0011.pdf1206? (page 5)

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:m16h5059u4rb2f0oljo6nvkns168r5eo4l@4ax.com...
|
| Would you believe 100nF/25V C0G in 1206? Not insanely expensive
| either.
|
| http://www.murata.com/catalog/c02/es0011.pdf1206? (page 5)
|
| Best regards,
| Spehro Pefhany
| --
| "it's the network..." "The Journey is the
reward"
| speff@interlog.com Info for manufacturers:
http://www.trexon.com
| Embedded software/hardware/analog Info for designers:
http://www.speff.com

Gosh! Zero tempco decoupling for the digital folks.

DNA
 
On Wed, 17 Mar 2004 18:21:12 GMT, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

On 17 Mar 2004 10:12:04 -0800, the renowned k7itm@aol.com (Tom Bruhns)
wrote:

Yeah, they're rolled up, but the contact is made across the ends,
generally, not just at one location in the roll. (That's why you
should build that vector network analyzer...) But I'd avoid them:
they can't take the heat. C0G ceramics and polyprops are both good.
C0G ceramics are available up to 10nF or so even in SMT; polyprops
down to 1nF at least and up to many uF.

Would you believe 100nF/25V C0G in 1206? Not insanely expensive
either.
Click to expand...
It's almost as if they can defy the laws of physics these days....
Next thing you know: 100A FETs in the same package. :-|
--

The BBC: Licensed at public expense to spread lies.
 
On Wed, 17 Mar 2004 15:45:34 -0000, "Emoneg" <Emoneg@nothere.com>
wrote:

"Paul Burridge" <pb@osiris1.notthisbit.co.uk> wrote in message
news:6afg50lhac3arueiodioejthtojlr3tten@4ax.com...
| Hi,
|
| They look worryingly inductive on visual inspection (there are metal
| foils rolled up in thar by the look of it.) And yet the CPC catalogue
| says that their properties make them ideal for use in filters. Has
| anyone any remarks (favourable or otherwise) to make about the use of
| this type of cap in filter apps?

Silly boy......
Click to expand...
Sorry. I'll try not to ask such *stupid* questions again.
--

The BBC: Licensed at public expense to spread lies.
 
On Wed, 17 Mar 2004 23:01:13 -0000, the renowned "Emoneg"
<Emoneg@nothere.com> wrote:

Gosh! Zero tempco decoupling for the digital folks.
DNA
Click to expand...
The Z5U parts pretty much magically disappear if you get them cold..
but X7R is good enuf.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
On Wed, 17 Mar 2004 12:03:06 +0000, Paul Burridge
<pb@osiris1.notthisbit.co.uk> wrote:

Hi,

They look worryingly inductive on visual inspection (there are metal
foils rolled up in thar by the look of it.) And yet the CPC catalogue
says that their properties make them ideal for use in filters. Has
anyone any remarks (favourable or otherwise) to make about the use of
this type of cap in filter apps?

p.
Click to expand...
They're great for LC filters. If you choose your ferrite right, you
can have a pretty stable filter over temperature. Problem is, not many
people make these any more. For production, avoid them due to
availability. If you're worried about inductance, that probably means
that you're in the MHz region which means you can use NPO (COG)
ceramic. Easier to get.

Mark
 
Behold, qrk signalled from keyed 4-1000A filament:

On Wed, 17 Mar 2004 12:03:06 +0000, Paul Burridge
pb@osiris1.notthisbit.co.uk> wrote:

Hi,

They look worryingly inductive on visual inspection (there are metal
foils rolled up in thar by the look of it.) And yet the CPC catalogue
says that their properties make them ideal for use in filters. Has
anyone any remarks (favourable or otherwise) to make about the use of
this type of cap in filter apps?

p.

They're great for LC filters. If you choose your ferrite right, you can
have a pretty stable filter over temperature.
Click to expand...
Air-core my good man, air-core ;-)

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca
 
"Paul Burridge" <pb@osiris1.notthisbit.co.uk> wrote in message
news:hknh509b1vrg6j33c8apcii0eeenirr9il@4ax.com...
On Wed, 17 Mar 2004 15:45:34 -0000, "Emoneg" <Emoneg@nothere.com
wrote:


"Paul Burridge" <pb@osiris1.notthisbit.co.uk> wrote in message
news:6afg50lhac3arueiodioejthtojlr3tten@4ax.com...
| Hi,
|
| They look worryingly inductive on visual inspection (there are metal
| foils rolled up in thar by the look of it.) And yet the CPC catalogue
| says that their properties make them ideal for use in filters. Has
| anyone any remarks (favourable or otherwise) to make about the use of
| this type of cap in filter apps?

Silly boy......

Sorry. I'll try not to ask such *stupid* questions again.
Click to expand...
no stupid questions, unless you ignored the answers last time.....

remember, things you know are easy. Its the things you dont know that are
hard.
 
"Emoneg" <Emoneg@nothere.com> wrote in message news:<WK46c.7336$2d4.2299@newsfe1-win>...

Gosh! Zero tempco decoupling for the digital folks.
Click to expand...
Don't laugh. Someone just today quite seriously suggested C0G bypass
caps for op amp power supplies for something I'm working on, and I'd
need at least 100nF for the task.

Cheers,
Tom
 
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