sine wave shaper

Discussion in 'Homework Help' started by lalalu, Aug 17, 2009.

  1. lalalu

    lalalu Thread Starter New Member

    Joined:
    Aug 16, 2009
    3
    0
    Hello all

    I am having trouble understanding a waveform shaping circuit that I found on the internet. [​IMG]

    My task is to generate a sine wave (adjustable low frequency range). My plan is to use a vco to generate triangular wave and then change it into a sine wave. I was thinking of using the breakpoint method, and then I found this circuit.

    So my question is what is the purpose of the opamp at the end? To smoothen the peak? or is this just aa normal feedback circuit. I also didnt get how the diodes work here, is this just a clipper circuit? I simulated the circuit in spice and found out that the circuit works just fine with only 2 diodes and 1 resistor (+side). Weird
    [​IMG]

    Anyway I would appreciate it if someone could explain to me how the circuit work, or at least just the name of the circuit. Searching sine wave shaper blindly these past few days didnt yield much result. Thank you
     
    #1
  2. jlcstrat

    jlcstrat Active Member

    Joined:
    Jun 19, 2009
    58
    3
    It would appear the opamp is just used to amplify the signal...The diodes clip the signal to give it more of a sinusoidal shape...I'm only a student myself, but that would be my best guess
     
    #2
  3. bertus

    bertus Administrator

    Joined:
    Apr 5, 2008
    13,836
    1,727
    Hello,

    The wave shape uses a kind of multiple break points to convert the triangle to a sinawave.
    In the two attached PDF's you will find wave shapers with diodes too.

    Greetings,
    Bertus
     

    Attached Files:

    #3
    umarfarooqleo likes this.
  4. Wendy

    Wendy Moderator

    Joined:
    Mar 24, 2008
    19,841
    1,962
    #4
  5. Audioguru

    Audioguru New Member

    Joined:
    Dec 20, 2007
    9,411
    886
    A ICL8038 and an XR2206 function generator IC uses multiple breakpoints with diodes to convert a triangle wave into a sine-wave with horrible distortion.

    The circuit that has only three breakpoints is much worse.
     
    #5
  6. Ron H

    Ron H AAC Fanatic!

    Joined:
    Apr 14, 2005
    7,050
    646
    The eyeball is not a great harmonic distortion analyzer.
     
    #6
  7. lalalu

    lalalu Thread Starter New Member

    Joined:
    Aug 16, 2009
    3
    0
    Ok thanks guys for the speedy response. Especially Brutus :).

    The pdfs link helps a lot.
     
    #7
  8. Wendy

    Wendy Moderator

    Joined:
    Mar 24, 2008
    19,841
    1,962
    Amen! Makes you appriciate HP equipment when you have access to it.
     
    #8
  9. Audioguru

    Audioguru New Member

    Joined:
    Dec 20, 2007
    9,411
    886
    You don't need an HP distortion analyser when the distortion is as high as the sine-wave made with a few breakpoints. You can hear the buzzing distortion.
     
    #9
  10. Ron H

    Ron H AAC Fanatic!

    Joined:
    Apr 14, 2005
    7,050
    646
    I was thinking more about the sine-like shape. All that golders is not glist, etc.
     
    #10
  11. Audioguru

    Audioguru New Member

    Joined:
    Dec 20, 2007
    9,411
    886
    A Cmos digital inverter that is self-biased can be used to smooth a triangle-wave into a pretty good looking sine-wave but its even harmonics are not as low as they should be.
    The inverter "compresses" the peaks of the triangle-wave.
     
    #11
  12. danny2

    danny2 New Member

    Joined:
    Oct 28, 2009
    29
    0
    by setting the Vsin is 50Hz,and VAMPL is 14V,AC=10V passing through the 1k ohm resistor.what is the frequency spectrum should be?is my simulate correct?
     

    Attached Files:

    #12
  13. Wendy

    Wendy Moderator

    Joined:
    Mar 24, 2008
    19,841
    1,962
    #13
  14. danny2

    danny2 New Member

    Joined:
    Oct 28, 2009
    29
    0
    ops..ya.wrong post.
     
    #14
  15. danny2

    danny2 New Member

    Joined:
    Oct 28, 2009
    29
    0
    how to generate the 50Hz frequency of this sine waveform?

    i had connect triangular waveform circuit to your circuit,i get the frequency of the 100Hz at the output of U3 in the schematic.

    i have done the calculation for the triangular generator.the formular is F=R1/4(C1)(R9)(R3).the value for R1=100k,C1=0.1u,R9=417k,R3=12k,the frequency obtain is 50Hz,but then when i simulate this circuit,i get the sinewave of 100Hz,doen't it suppose to follow the triangular frequency?I need help on this.
     

    Attached Files:

    • sine.JPG
      sine.JPG
      File size:
      139.1 KB
      Views:
      92
    #15
  16. Audioguru

    Audioguru New Member

    Joined:
    Dec 20, 2007
    9,411
    886
    Why do you have so many threads about this same circuit?
     
    #16
  17. danny2

    danny2 New Member

    Joined:
    Oct 28, 2009
    29
    0

    am i?i only create 1 topic on this matter.
     
    #17
Loading...
Similar Threads
  1. Teena123
    Replies:
    18
    Views:
    1,314
  2. Cerkit
    Replies:
    2
    Views:
    1,108
  3. Yoda
    Replies:
    9
    Views:
    1,643