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Variable capacitor circuits

Discussion in 'General Electronics Chat' started by walters, Jan 13, 2006.

  1. walters

    walters Banned

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    just self taught with some books

    do u know the formulas i need please
     
  2. _3iMaJ

    _3iMaJ New Member

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    Using a formula isn't the answer. Understanding the "why" will answer the "how."
     
  3. mstechca

    mstechca New Member

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    Why do you care?
    I think walters needs this question asked to him again:

    What are you trying to achieve?

    I mean why would you want one formula for input, RC time, and phase? To me it is senseless to try to combine everything into one formula.
    I only look at the RC time. Input is just input. and if the input is a speaker, check it's resistance, and then treat it as a resistor.
     
  4. dave

    Dave New Member

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  5. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The low frequency resonance of a speaker causes it to be a lousy microphone.
    Try making an allpass filter, a variable phase shift or a comb filter with just a speaker.

    I know what you can do with the speaker: spin it! :lol:
     
  6. mstechca

    mstechca New Member

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    Why do you care?
    In fact, connect a speaker to a circuit of some sorts, and to a motor, and see if you can power the motor from the techno music in the room! :lol: :lol:
     
  7. walters

    walters Banned

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    Are Varactors a reversed bias Zenor diode or a regular diode?
     
  8. walters

    walters Banned

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    varactor diodes the capacitances are in the picofarads

    Can i use Varactors in "series" to increase the capacitances?

    Or i would need a "Custom" Varactor diode to have the capacitance in the microfarads?

    What would the Varactors doping process do different and how? the PN junction needs to be Bigger?


    I need a Varactor is the Mircofarads? which ones is there please?
     
  9. akg

    akg New Member

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    varactors a reverse biased diodes with specific dopping to act it as 'varactor' .
    and u cannot (practicaly)get a uF varactor.
    hava a look at
    http://en.wikipedia.org/wiki/Varactor
    http://www.vias.org/simulations/simusoft_varactor.html
    http://www.play-hookey.com/semiconductors/specialized_diodes.html
     
  10. walters

    walters Banned

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    thanks for the help

    How can i get a a uF varactor?

    I need uf Varactors?

    How can i make one or put them in series or so to make a uf varactor?
     
  11. akg

    akg New Member

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    u cannot (practicaly)get a uF varactor. afaik
     
  12. walters

    walters Banned

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    why not?
     
  13. akg

    akg New Member

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    it requires a large depletion layer region (large area).
    Also varacters are used in HF/UHF ckts for tuning , that reqs only pf variation
    i hope u have visted the links i suggested.
     
  14. walters

    walters Banned

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    So i have to get this Custom made to have a large depletion layer region (large area)?
     
  15. akg

    akg New Member

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    AFAIK
     
  16. walters

    walters Banned

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    A large depletion layer region large area would give me more capacitance to be mircofarads?

    Most Varactors are used:
    tunable filters and oscillators , frequency multiplication and frequency mixing
     
  17. akg

    akg New Member

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    walters
    u have a 1000 1PF capacitors , how would u make a 1uF capacitor out of it?
     
  18. walters

    walters Banned

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    put another one in series? or 3 or 5 in series? to ADD them?
     
  19. akg

    akg New Member

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    if u have got some capacitor and a measurement eqp: , try it out and check what happens.
     
  20. walters

    walters Banned

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    Yea but i still can't Vary the Varactors in Mircofarads i need to have a variable .01uf or .47 or 220uf Varactors i wish they made these

    I need to use the .01uf Varactors in a phase shift network filter for audio not radio
     
  21. akg

    akg New Member

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    audioguru wrote :
    Repeat
     

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