Problem with RC Wien oscillating generator...

Discussion in 'The Projects Forum' started by johnymo, Jan 24, 2009.

  1. johnymo

    Thread Starter New Member

    Jan 24, 2009
    3
    0
    Hi,
    I am designic a RC Wien oscilating generator,that would have Total Harmonic Disortion < 1%,and this is my main problem.
    My circuit shold generate:
    1Hz-20Hz: R<0-1,5k> C=51u
    20Hz-200Hz: R<0-1,5k> C=5.1u
    200Hz-2kHz: R<0-1,5k> C=510n
    2kHz-20kHz: R<0-1,5k> C=51n
    I am designing in PSpice 9.2,what is my main problem?
    Thank You very much for any answer
    Regards
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    Can you post a normal schematic (best in png format, jpg is lossy) ?
    I can not use the files in the zip.

    Here is a page from the EDUCYPEDIA on sinewave oscillators.
    http://www.educypedia.be/electronics/analogosciltypes.htm
    Wien bridge oscillators are down the page.

    Greetings,
    Bertus
     
  3. johnymo

    Thread Starter New Member

    Jan 24, 2009
    3
    0
    My schematic i-png in attachement.
    Thank you
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    You are trying to use an AGC with your oscillator.
    Look at figure 15-12 in the attached PDF, for some background information.
    (this example is for single supply)

    Greetings,
    Bertus
     
  5. kahafeez

    Active Member

    Dec 2, 2008
    150
    0
    i suggest u use this schematic..... it works perfect i've used it abt 5 times..... and its the simplest.... works upto 100KHz if ur amplifier is a TL071 or TL072....
     
  6. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    What kind of distortion do you see ?
    Is the sinewave clipped ?
    Of so the feed back of the AGC is not correct.

    Greetings,
    Bertus
     
  7. johnymo

    Thread Starter New Member

    Jan 24, 2009
    3
    0
    The THD is about 4-5 %, the sinewave is not cot by amplifier,maybe the problem is realy is AGC calculations, my Ugs was -0,6V.
     
  8. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    Perhaps you could try to replace R34 by a potentiometer of 25K.
    You can measure the distortion with different settings and see what the optimum is.

    Greetings,
    Bertus
     
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