what capacitor type is best used on Carlosfm's non-inverting chipamp? - diyAudio
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Old 22nd August 2007, 05:58 AM   #1
jarthel is offline jarthel  Australia
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Default what capacitor type is best used on Carlosfm's non-inverting chipamp?

This is not the latest but it would be close: http://www.diyaudio.com/forums/attac...amp=1112492461

I'm looking at C3, C5, C7 and C8.

Thank you very much.
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Old 22nd August 2007, 10:54 AM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
metallised film caps could be used in all locations.
Polypropylene(PP) or Polyester(PES) would do.
You may find that low K ceramic will work, but you really must experiment if you try ceramic. Ceramic are generally smaller and cheaper. PP are generally bigger and dearer.

Some builders will suggest better quality caps for the decoupling around the chipamp. This applies to both the electrolytic and the bypasses. But again carefull experimentation and measurement should be carried out to ensure that ripple and oscillation on the supply rails is avoided.
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Old 22nd August 2007, 11:54 AM   #3
jarthel is offline jarthel  Australia
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I have been searching and it seems polypro are inductive which is bad when use as a bypass caps (which I believe C3 and C4 are)?
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Old 22nd August 2007, 02:02 PM   #4
AndrewT is offline AndrewT  Scotland
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Hi, polystyrene are usually rolled foil and these are definitely inductive.
Most makers of PP claim they make PP in a non-inductive form.

The obsolete stacked film polycarbonate were excellent in this respect, but nothing seems to be available to match the performance/cost ratio of these. The cheaper PP are getting close but tend to take up more space.
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Old 22nd August 2007, 03:11 PM   #5
rdf is offline rdf  Canada
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Quote:
Originally posted by jarthel
I have been searching and it seems polypro are inductive which is bad when use as a bypass caps (which I believe C3 and C4 are)?
Wima's site has excellent technical information on this aspect. Cole's Notes edition IIRC: the inductance of a modern film cap is almost entirely determined by it's lead-to-lead dimension and is on the order of an equivalent length piece of wire. In other words at the limits of physics in a three-dimensional world.
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Old 22nd August 2007, 11:58 PM   #6
jarthel is offline jarthel  Australia
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Quote:
Originally posted by rdf


Wima's site has excellent technical information on this aspect. Cole's Notes edition IIRC: the inductance of a modern film cap is almost entirely determined by it's lead-to-lead dimension and is on the order of an equivalent length piece of wire. In other words at the limits of physics in a three-dimensional world.

thank you. I was looking at the datasheet and cannot find such info.
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Old 23rd August 2007, 12:03 AM   #7
Magura is offline Magura  Denmark
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Quote:
Originally posted by jarthel
I have been searching and it seems polypro are inductive which is bad when use as a bypass caps (which I believe C3 and C4 are)?

Yes, you are right....or would be right, if you were to design a radar or the like.

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Old 23rd August 2007, 12:06 AM   #8
rdf is offline rdf  Canada
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Quote:
Originally posted by jarthel
thank you. I was looking at the datasheet and cannot find such info.
Not on a datasheet, ask and ye shall receive:

http://www.wima.com/EN/selfinductance.htm
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Old 24th August 2007, 12:12 AM   #9
jarthel is offline jarthel  Australia
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Quote:
Originally posted by rdf


Not on a datasheet, ask and ye shall receive:

http://www.wima.com/EN/selfinductance.htm

thank you
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