From: Kevin McMurtrie
Subject: Re: Wrestlemania Royale: Tantalum vs. Electrolytic Vs. Polys, etc.
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Date: Fri, 25 Oct 2002 07:51:55 GMT
NNTP-Posting-Date: Fri, 25 Oct 2002 00:51:55 PDT
In article ,
email@example.com (Bob Wilson) wrote:
>In article ,
>>On the subject of capacitors in a nutshell, what are the main
>>selection points why one would choose say an electrolytic over a
>>tantalum? i.e. Aside from ESR criteria, in say a decoupling situation
>>on the power supply pins of an op-amp, what would be the couple of
>>reasons why one would choose electrolytic over tantalum or vice versa?
>>And on that same note, say the same op-amp used in a simple amplifier
>>scheme with a HF rejection cap across the feedback path, what would
>>you choose there, polypropylene, polyester, ceramic, foil, etc. and
>>why? And say in a digital scheme on the decoupling caps, what
>>there... ceramic...metalized polyester film... etc.?
>>While on the subject of caps, why not discuss resistors too. Metal
>>oxide film, carbon film or carbon composition?
>>Given an unlimited budget on a circuit design, what are the high
>>performance materials in the way of capacitors and resistors that one
>>would use in say an audio amplifier circuit or a high speed digital
>>I say the most colorful components are the ones that are the most
>>worthy of selection.
>Well, one good reason is that tantalums should NEVER be used as power supply
>filters unless there is some series impedances. Tantalums are subject to
>catastrophic failure from excessive dV/dt.
>Another obvious reason is cost. Tantalums cost far more than electrolytics.
Mining tantalum can be environmentally destructive too. It's close to
the surface so bandits can rip out big chunks of the earth and run.
I find that tantalum caps are best used as low voltage local power
supply decoupling capacitors. I use electrolytic for the main power
supply, Mylar caps for high voltage supply decoupling, and ceramics for
most analog processing. There are no hard rules, of course.
The Art of Electronics has a nice guide on different component