Is there a Unipolar Capacitor???

[ultradust]

Hello... I'm just wonderin' if there is really a unipolar capacitor??? Is it electrolytic? Tantallum? Metal film? Where can I find one and what does it look like??? THanks...

[Peter Snowberg]

All unipolar caps are called "polarized". The most common ones are Tantalum and Aluminum Electrolytic.


Metal film caps are non-polarized.

[ultradust]

All unipolar caps are called "polarized". The most common ones are Tantalum and Aluminum Electrolytic.


Metal film caps are non-polarized.

AAAwww... That's why I can't find one in the google??? THanks for the help...  

[Mark F]

Ummm...Aren't all caps by their very nature bi-polar? Bi meaning 2. Uni meaning 1. If something is unipolar wouldn't it have but one lead? I may be way off base here but it just jumped out at me..uni=1 and caps always have 2 leads.  :? Non-Polarized may not have + and - terminals but I think they still have two poles. Just thinking out loud.

[R.G.]

Ah the beauties of English, where any word can be any part of speech. Even a noun can be verbed.

In the context of electronic capacitors, "polar" means that the voltage across the device matters as to direction. One lead is to be more positive than the other. NON polar means that the voltage direction of one lead compared to the other does not matter.  BI-polar is a corruption for electrolytics that have had oxide grown to resist both directions of voltage application. I guess there is some sense to it in that a bipolar electrolytic is really an electrolytic grown to have two positives or two negatives, so that which is which doesn't matter in actual application.

By that line of reasoning, NON polar should never be applied to electrolytics at all, because there really isn't any non polar electro. Bipolar is what you get. By strenuous reasoning, I'd suppose that non polar only applies to capacitors that don't have any implied polarization, like all the poly film caps.  Polarity just doesn't matter to them.

One could stretch the language a bit to call ordinary polarized electros UNI-polar because they have to be used with voltage one way, but English being what it it, that carries the nuance that there may only be one lead, which is incorrect. And it's unnecessarily duplicative, since "polar" means and implies what is meant, no funny nuances.

[Mark F]

Thanks RG! :wink: