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There is one small problem in my understanding of polarized capacitors.

The thing is that when using polarized capacitor, you should apply positive voltage terminal to anode and negative voltage terminal to cathode, otherwise it gets destroyed. But can a polarized capacitor survive when AC voltage is applied, where the polarity of source generator is constantly changing, therefore half of the period capacitor is polarized the wrong way, so in that case capacitor would be destroyed? -> in case of capacitor applied directly to AC generator.

I know that for polarized cap, the "reverse voltage" can be as high as 2V for some period of time and the cap still survives it.

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  • \$\begingroup\$ AC will almost always destroy a polarized capacitor not designed for it, granted it may take slightly longer than applying DC in reverse. It all happens so quickly, though, you probably wouldn't notice the difference \$\endgroup\$ – DerStrom8 Sep 5 '17 at 14:07
  • \$\begingroup\$ If you must be able handle AC without a DC bias you can either get a non-polarized capacitor (obviously) or (poor man's solution) use two polarized caps in anti-series, meaning both negative sides connected, AC signal across both positive terminals. Do use identical capacitors though. I would only use this for small signals, not for transferring power over AC. \$\endgroup\$ – Bimpelrekkie Sep 5 '17 at 14:13
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You can't do that — or at least, you shouldn't. When polarized capacitors are used to couple AC signals, there is normally also a DC bias across them that keeps the net voltage (DC plus instantaneous AC) from ever going negative.

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  • \$\begingroup\$ So when DC bias is also applied, the polarization of capacitor depends on DC bias, and not AC? \$\endgroup\$ – Keno Sep 5 '17 at 15:48
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    \$\begingroup\$ As I said, the net polarization at any given instant in time is the sum of the two. As long as the positive DC bias is greater than the AC's peak negative value, you're good to go. \$\endgroup\$ – Dave Tweed Sep 5 '17 at 15:49

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