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Varicap @ mV or even µV?

Discussion in 'General Electronics Discussion' started by Moritz, Dec 12, 2015.

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  1. Moritz

    Moritz

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    Dec 12, 2015
    Hi there,

    I'm curious. Do varicaps exists, that can operate with mV or even µV?
    And what should I search for?

    Thanks and best regards,
    Moritz
     
  2. davenn

    davenn Moderator

    13,833
    1,950
    Sep 5, 2009
    hi there
    varicap diodes, I assume you are referring to ?

    what is your application ?
     
  3. Moritz

    Moritz

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    0
    Dec 12, 2015
    Yes, I'm referring to variable capacity diodes.

    And I can't really tell you what I'm intending to do. Junst wondering if there are any, that can change theire capacity by milivolts of DC bias?
     
  4. davenn

    davenn Moderator

    13,833
    1,950
    Sep 5, 2009
    you would have to look at the datasheets for specific types to get an idea
    of their change in capacitance relative to the voltage ... that data will be graphed
    and they will all be different


    Dave
     
  5. Moritz

    Moritz

    3
    0
    Dec 12, 2015
    Yeah, I know that, that's why I'm asking. Because the datasheets I previously looked at don't have any data below several hundred of milivolts. So I'm wondering if maybe you guys know some varicaps that can operate in such magnitude of voltage...
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
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    Jan 21, 2010
    well, they will very definitely resound to a signal in the millivolt or microvolt range, but this would need to be added to a constant voltage, and the amount of variation would be tiny.

    Amplifying that small signal before applying it tho the diode would allow you to change the capacitance more.

    The reason you need a relatively large voltage change to affect the capacitance is that you don't want the signal itself to change the capacitance (typically).

    If your control voltage was significant at a might change then your signal would need to be even smaller.
     
  7. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    Moritz,
    What is the frequency range you are going to operate at?
     
  8. davenn

    davenn Moderator

    13,833
    1,950
    Sep 5, 2009
    asked him for application and got this as a reply .....


    cant ?, don't want to ? something else ??
    If you want our help, you need to help us in a better way


    Dave
     
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