Orcad pspice thd vs. Frequency response

Discussion in 'Homework Help' started by PowerAmp_, Nov 8, 2013.

  1. PowerAmp_

    Thread Starter New Member

    Nov 8, 2013
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    Hi folks!

    I want to plot the THD vs. Frequency Response of an Amplifier Stage in Orcad Pspice!

    Does anyone know how that runs?!

    Thanks in Advance!

    Best Regards
    PowerAmp_
     
  2. LvW

    Active Member

    Jun 13, 2013
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    100
    I am afraid, this is not possible.
    The THD is a parameter that contans non-linearities of the device and, in contrast, the AC analysis (which is the only one showing the frequency on the horizontal axis) is a linear analysis.
    I think, there is no way out than to determine the THD for different frequencies running different TRAN analyses.
     
    Last edited: Nov 9, 2013
    PowerAmp_ likes this.
  3. PowerAmp_

    Thread Starter New Member

    Nov 8, 2013
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    Hi LvW!

    Thanks for your statement!

    I bought the book "Small Signal Audio Design" by Douglas Self and in the book there are plots of THD vs. Frequeny Response!

    Maybe he is using another SPICE programm or uses other ways to plot them!

    When I have found out how does it run i will post it here!

    Best Regards

    PowerAmp_
     
  4. t06afre

    AAC Fanatic!

    May 11, 2009
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    I think you need to analyse a real system. To get those numbers correct. What you can do is to run transient analysis to get an idea then clipping occurs. Clipping will affect the THD numbers in a drastic manner.
     
  5. t06afre

    AAC Fanatic!

    May 11, 2009
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    Looking in the book. I think most of the charts of that kind. Are made by eqipment from this vendor http://www.ap.com/products
     
  6. PowerAmp_

    Thread Starter New Member

    Nov 8, 2013
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    Hi!

    Probably he did it with some equipment like that!
    Unfortunately I think there is no way to do that in Pspice!

    Best Regards

    PowerAmp_
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
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    After some use of Google I found this
    In TRAN setup you have to activate FOURIER and to specify the fundamental frequency of the signal you want to analyze as well as the corresponding node voltage. After completion of the analysis the result (THD in %) is written in the *.out-file.
    I have not done these kind of analysis my self. The result from this analysis would probably not reflect the real world situation in a good manner. The analysis you want to do is THD+N(N=noise). And such type of analysis will only have a value then done on a real world system. But good luck with your project
     
  8. PowerAmp_

    Thread Starter New Member

    Nov 8, 2013
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    0
    Ok,
    The THD in the output file is well-known by me.
    Between real world and simulation is always a big difference! :D
    I think I can continue my project without THD+N(%). ;-)

    Best Regards
    PowerAmp_
     
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