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Are some capacitors LOW ESR????

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russwr

Dec 20, 2019
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How to tell capacitors that are low ESR???? Brand type, color, imprinted??? Unverified?
 

Harald Kapp

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All caps you buy are low ESR
This is definitely wrong.
Especially when it comes to electrolytic capacitors. That is the reason why dedicated "low ESR" types are available at a higher price for use e.g. in power supplies to reduce power dissipation due to AC ripple.
 

Harald Kapp

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You may as well just consider capacitors pure shorts.
Seems you have a misconception about how capacitors work. Try this tutorial.
A capacitor works like a short circuit only at the first instance when it is not yet charged and a voltage is applied. Once the capacitor starts charging, the current is reduced until it is zero once the capacitor is fully charged.
If a capacitor were a pure short, nobody would place it across the power supply rails of a circuit.
 

hevans1944

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Jun 21, 2012
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All caps you buy are low ESR, high ESR caps are completely different, like when your measuring capacitance out of random things.
like when your conducting a whole heap of home made semiconductor mush, when you get your series resistance.
This post is nonsense. Capacitors are not intentionally manufactured with high electrical series resistance (ESR). High ESR can be caused by age, method of lead attachment, and the technology used to establish an insulating layer between the two capacitor electrodes.

In general, electrolytic capacitors DO have higher ESR than non-electrolytic capacitors that use paper, glass, plastic film, mica, vacuum, or ceramics for insulation between the two capacitor plates before the external electrodes are attached. The ESR of electrolytic capacitors increases as a function of frequency, which is why power supply by-pass or "filter" capacitors often consist of an electrolytic capacitor wired in parallel with another type of capacitor with a known, lower, ESR.

Special "low ESR" electrolytic capacitors, as @Harald Kapp mentioned in his post #5, are often used to reduce the "ripple current" in power supplies because this current heats the capacitor and can lead to early failure of the electrolytic dielectric insulation.

And just what, exactly, is "a whole heap of home made semiconductor mush?" It doesn't seem to correspond to any definition of mush that I can find after a quick search on the Internet. Most respondents, at least those whose posts I consider valid, will upload comments that are both relevant and trustworthy. Your posts seldom satisfy either criteria.
 
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