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I am studying the schematic for a reactive load box - a device which can be plugged into a guitar amplifier instead of a speaker, on the website http://www.aikenamps.com/index.php/designing-a-reactive-speaker-load-emulator .

The circuits uses a 'bipolar' capacitor - a component i have previously not heard of. I am familiar with parallel-plate capacitors and electrolytic capacitors, and the physics of them both but the mention of a bipolar cap has confused me. There are debates online about creating a cap from two bipolar caps connected head to head, but there doesn't seem to be much on the component itself.

  • What is it
  • What notable uses does it have?

Thanks

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Bipolar is not commonly used these days (outside of psychiatric circles, of course). The more common term is unpolarized. This is in contrast with polarized capacitors such as electrolytics, where applying the wrong polarity can destroy the cap.

So a bipolar label is typically used to draw attention to a cap whose value is so large that a polarized cap might be expected, but which must not actually be polarized.

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  • \$\begingroup\$ Agreed. I typically see bipolar in reference to non-polarized electrolytic capacitors - used where the larger value is impractical for ceramics, but polarized electrolytics are not recommended. \$\endgroup\$ – Jay May 10 '17 at 16:21
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A bipolar capacitor is just a non-polarized capacitor. I think the term is usually in reference to a type of electrolytic capacitor to make it clear that you can use it in any orientation since they're usually polarized. I don't think they're otherwise special. At a high-level you could replace it with a ceramic capacitor of the same capacitance. The important part is that they seem to think it is important to use a non-polarized capacitor that is 100 uF. A ceramic equivalent would be pretty expensive if you could find it.

That said, unless they expect "ground" to go above the "input" I see no reason why you couldn't use a polarized electrolytic cap.

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    \$\begingroup\$ Given that this circuit is designed to take the place of a speaker I'd expect ground to spend nearly half of its time above the input... \$\endgroup\$ – Finbarr May 9 '17 at 23:53

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