Loop Filter with Negative Resistance in PLL

Discussion in 'General Electronics Chat' started by lkgan, Mar 14, 2011.

  1. lkgan

    Thread Starter Member

    Dec 18, 2009
    117
    0
    Hi,

    I have read about what is negative resistance all about in wikipedia. It doesn't exists in real components. It can be synthesized using op-amp (as what I have read in wikipedia):

    http://en.wikipedia.org/wiki/Negative_resistance

    How can a negative resistance effect a circuit in real application? Anyone has tried on a real hardware?

    Regards,
    lkgan
     
    Last edited: Mar 14, 2011
  2. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    I simulated it in this: http://www.falstad.com/afilter;

    Interestingly, it seems the response is identical frequency wise, but the phase response is reversed.
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Actually negative resistance not only exists, but is very common. Neon bulbs, tunnel diodes, and many more devices have regions of negative resistance in their characteristic curves. It is the principle behind a relaxation oscillator.
     
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