Phase Locked Loop

Discussion in 'Homework Help' started by Ashu93, Nov 16, 2012.

  1. Ashu93

    Thread Starter New Member

    May 2, 2012
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    My teachers told me that the output of PLL circuit is same as its input but i am not able to understand if the output of PLL is same as its input then why we are using it... Please help:confused::)
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Well your teachers told you wrong. It depends on the context of the question and situation.
     
  3. crutschow

    Expert

    Mar 14, 2008
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    The output and input will be in phase but they have different frequencies. Thus you can generate an output frequency that is some multiple of the input frequency. If the input is from a crystal oscillator you can generate accurate output frequencies with the accuracy determined by the oscillator accuracy. That's how frequency synthesizers work.
     
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Input and output can have the same frequency. As an example, a PLL with a VCXO can stabilize a jittery or noisy input signal.
     
    Last edited: Nov 16, 2012
  5. bertus

    Administrator

    Apr 5, 2008
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  6. crutschow

    Expert

    Mar 14, 2008
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    I somehow figured someone would come up with an exception to my generality. ;)
     
  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    There is also a system that locks on any multiple of the reference, called the Huff and Puff VFO stabilization.
    Hans Summers has a couple of examples here:
    http://www.hanssummers.com/huffpuff.html

    Bertus
     
  8. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Yeah, leave it to the old nitpicker.:D
     
  9. justtrying

    Active Member

    Mar 9, 2011
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    I liked this tutorial when I tried to grasp PLLs.
     
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