need help in this schematic (function generator)

Discussion in 'The Projects Forum' started by endaya_walatch, Oct 23, 2009.

  1. endaya_walatch

    Thread Starter Member

    Sep 13, 2009
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    hi.. i would like to ask about the purpose of each component in this schematic.. hope you can help me.. please..

    thanks..
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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  3. Audioguru

    New Member

    Dec 20, 2007
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    It is not a function generator. It is a poor sine-wave generator.
    It needs another opamp as a buffer so that the third RC network is not loaded down by the 7.5k and 20k resistors of the inverting amplifiers.

    It does not have an amplitude limiting circuit so its output will be clipped.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    You seem to be on an endless quest for a function generator. This is about the 5th thread you've started for this (more?). Did the others we went over not work, or are you trying to understand oscillators?

    There are chips that will do this, though they are a bit more complex in parts.
     
  5. endaya_walatch

    Thread Starter Member

    Sep 13, 2009
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    oh...thanks for the immediate reply.. by the way, i'm still curious about how to get the frequency in this circuit?? can you help me again?
     
  6. endaya_walatch

    Thread Starter Member

    Sep 13, 2009
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    yup.. i have a difficulty in understanding those schematic so i prefer to study one by one...
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    You need to learn how a phase-shift oscillator works in Google or ask your teacher.
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    Wikipedia has a pretty good article on phase shift oscillators. Basically each RC leg shifts the target frequency 60°. Do this three times and you have 180°. Add an inverting amplifier for another 180° phase shift and you have positive feedback, which all oscillators need. The reason it is a sine wave oscillator is only one frequency will shift 60° in each RC leg, all other frequencies don't meet this mathimatical requirement.
     
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