Purely cubic capacitor

Discussion in 'General Electronics Chat' started by circuit_non, May 9, 2014.

  1. circuit_non

    Thread Starter New Member

    May 9, 2014
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    Hello,

    I am wondering if it is possible to implement in circuit a capacitor which has the following voltage-charge relationship:
    V(q)=C*q^3

    Note, it is important that there is no linear term in there (i.e. I don't want a*q+C*q^3) etc.

    Thank you.
     
  2. wayneh

    Expert

    Sep 9, 2010
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    It would be possible if there were such a thing.

    Possible doesn't mean useful. I suppose there must be some niche application in which this behavior would be useful.
     
  3. circuit_non

    Thread Starter New Member

    May 9, 2014
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    Yes, I have application in mind. Do you know how to implement it or can you provide some sources ?
     
  4. wayneh

    Expert

    Sep 9, 2010
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    Oh, that's a different question. I know of no such thing. Depending what you're up to, you could get a microprocessor to simulate that behavior, i.e. to act like your hypothetical capacitor.

    I think there is also such a thing as a voltage multiplier circuit in the analog world. You need (V/C)^3.
     
  5. Adanovinivici

    Member

    Sep 5, 2014
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    Well, analog circuits were originally used to solve differential equations, so I'm sure there is a way to obtain that relationship. It seems like you know the circuit is going to be non-linear. I did some research and I don't think a capacitor will give you that relationship. However, you could use op-amps and diodes to do it. You may have to remove a linear term using a summing amplifier though. If your using a breadboard don't forget to attach capacitors across the voltage supply (I read a post that mentioned this).

    You could chain two integral amplifiers together with a triangle wave input and you would obtain cubic sections if that's what your looking for.
     
  6. Adanovinivici

    Member

    Sep 5, 2014
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    I used is http://en.wikibooks.org/wiki/Electronics/Analog_multipliers to get an idea of the type of analog circuit needed.
     
  7. wayneh

    Expert

    Sep 9, 2010
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    Year old thread!
     
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