Op-amp square wave generator

Discussion in 'Homework Help' started by addleme, Dec 21, 2008.

  1. addleme

    Thread Starter New Member

    Dec 16, 2008
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    0
    Hello everyone, im going to use this circuit in my laboratory design project and represent the duty cycle as an output. My problem is that as a final report they want the analysis of the circuit we used. Thus I need an analysis of the Op-amp square wave generator part. I will be happy if anyone could analyse the circuit and write the frequency and duty cycle dependence on circuit component as mathematical expressions. Thank you very much..
    [​IMG]
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Keyword : Hysteretic Oscillator

    Look it up on Wikipedia. I have an article about a similar approach here.

    The AAC book also has a chapter on it here.
     
  3. steveb

    Senior Member

    Jul 3, 2008
    2,433
    469
    If you study comparator circuits with hysteresis using positive feedback, you will easily be able to develop the analysis of this circuit.
     
  4. Audioguru

    New Member

    Dec 20, 2007
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    896
    The lousy old 741 opamp is 40 years old this year. It is too slow for a square-wave generator. Frequencies above only 9kHz will be a low level triangle-wave.
     
  5. Mu86neer

    Member

    May 1, 2009
    23
    0
    hi there
    i tried ur circuit and it didn't oscillate,, r u sure its the correct one
     
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Many old 741 opamps do not work when the supply is only 5V. Try 12V or 15V.
    Turn the positive feedback pot for a high amount of positive feedback and turn the negative feedback pot for a low amount of negative feedback.
    Adjust the reference voltage pot to half-way.
    Then it will oscillate.
     
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