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Non-Polarized Electrolitic Capacitor w/diode bypass...

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spike6

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non polarized capacitor

Non-polarized Electrolytic Capacitor:
A non-polarized electrolitic capacitor can be made by connecting two normal electrolitics back to back. However, does not this connection half the capactance of the pair? For example if I connect two 6800uf caps back to back is not the total circuit capacitance now 3400uf? However, if each cap is paralleled by a diode such that the back-biased cap is bypassed by its parallel diode would not this restore the full capacitance of 6800uf to the circuit and minimize the reverse voltage load on the back-biased cap as well?
 

non-polarized electrolytic capacitor

Yea -- you are right, except you would see a diode drop in voltage, so the cap would only be good for unipolar applications -- what I mean is, consider what happens when you apply a large sine wave across the cap -- you only have conduction of the diodes when the signal is bigger than 2 diode drops -- it's a lot like the crossover distortion encountered with a class-B amplifier.

Added after 1 hours 16 minutes:

Actually, I was thinking about diodes in series with the caps, and then those two branches in parallel. Sorry.... But I think the diode drop issue is still valid in general - you might still run into problems if you need to couple a large signal AC (i.e. bigger than 1-2 diode drops) voltage through the cap.
 

make non-polarized capacitor

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lladnar23 -- Thanks for the reply.
I neglected to mention that my considered app is DC only, it's just that the DC poliarity gets reversed from time to time. So maybe it would still work OK.
 

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