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Problem with PWL option

spanika kamuni
Intellectual 370 points
Other Parts Discussed in Thread: TINA-TI

hii,

I have Problem measuring power across PWL source. I always see that the power measured across PWL source is in Terms of picoWatts. why is it so.....

signal.TSChere I have made a small Experiment where, I have choosen directly a sine wave option as Signal to one of the op amps and

a PWL Signal(sine wave in Terms of voltages and time) as a Signal to another op amp.

Now when I measure power at each source I find the power across PWL Signal to be in Terms of picoWatts and the power across sine Signal to be in Terms of milliWatts. why is it showing This way.

sine+PWL.TSCThis file explains what i meant in a better way. what ever I enter into PWL it always Shows power in picoWatts only

  • 0
    TI__Genius 13935 points
    Hello Spanika,

    Are you using AC analysis? If so AC analysis only allows one signal source. For some reason it looks like TINA is not treating the PWL input as an AC souce. I am not sure what the solution for this is. I will need to look into this more.

    You may just have to use the internal sine source for calculating power unless I can figure out why the PWL is not working.



    Regards,
    Loren
  • 0 in reply to Loren Siebert 1
    Intellectual 370 points

    Hello,

    Yes I want to perform ac analysis since I have a transformer in my later schematic.

    I want to use PWL as my source and I am concerned with the power at my source in particular. How can I solve this.

  • 0 in reply to spanika kamuni
    Intellectual 370 points
    What do you mean by internal sine source? This is not only the case with PWL. Except the sine and cosine, all the other signals show a 0 power when I put in a powermeter at source.
    Actually I wanted to use PWL as a noise source for my purpose
  • 0 in reply to spanika kamuni
    TI__Genius 12631 points
    Hello Spanika,
    It looks like you are simulating "AC Table Results" and then looking for the power in the table. I tried the simulation using an actual sine-wave source and that works like I expect. If I however take your PWL source with it 1.414Vp/333 kHz sine wave I don't get the correct value. This could be a bug in TINA.
    What you can do is to -
    1. Run a transient simulation.
    2. Extract the power meter output to a text file.
    3. Use the data in excel to calculate the standard deviation of the output waveform to find the rms power.

    I will look into this a little bit more and see if I can resolve the bug without you having to do the data extraction.
    -Samir
  • 0 in reply to spanika kamuni
    TI__Genius 13935 points

    Hello Spanika,

    First, I found that the frequency of the PWL function is 0.016Hz.  This may have some bearing on the power readings you are getting.

    Second, AC simulations will only give you relative power, not absolute.  AC simulations are by definition small signal analysis.  You can't do AC simulations with a PWL source, you need to use one TINA signal source (TINA won't process multiple sources in AC simulations).

    You will need to do transient simulations if you want to calculate power levels.  I ran a transient simuation with a 100 second time span and got reasonable results on the PWL source.  I think the problem is just the frequency is so low the source is near zero for a long time.


    Transient simulations will work with transformers, so you can run the whole system in a transient simulation. 

    From TINA help:

    When you select the Piecewise linear waveform you must specify the time-voltage/current pairs which describes the corner of the waveform. The values must be entered according to the PSpice syntax. Time and value scale factors can be used.

    You used integer seconds for your PWL function time/voltage pairs.  If you want a faster signal you'll need to divide the time numbers appropriately. 

    Regards,

    Loren

  • 0 in reply to Loren Siebert 1
    TI__Genius 13935 points

    PWL Sine.xlsx

    Hello Spanika,

    Here is an excel file that will modify your PWL function so that you can get the frequency you want.  Type your desired frequency in the yellow box, then you can paste the values into the PWL function in TINA.

    Regards,

    Loren

  • 0 in reply to Loren Siebert 1
    Intellectual 370 points
    thank you Loren. I didnot understand the Excel file you sent me. but then I converted the transient Analysis into the text file as you said and it Servers my purpose.
    Now I could solve the Problem of finding power at my load. But I want to find the gain vs freq (ac Response) also
    with this pwl source. is it possible.....
  • 0 in reply to spanika kamuni
    TI__Genius 13935 points
    Hello Spanika,

    If you want to do an ac analysis you need to use the built in AC source in TINA. If you want to get the gain for a PWL source you must use a transient analysis. This is just how the modeling works. This is universal to SPICE based software, it is not unique to TINA-TI.

    I am going to move this thread into the modeling forum. This forum is specific to high speed amplifiers, not SPICE modeling.

    Regards,
    Loren