PSPICE help

Discussion in 'Homework Help' started by Spoder, May 12, 2014.

  1. Spoder

    Thread Starter New Member

    May 12, 2014
    6
    0
    Hi there everyone,
    I'm currently busy trying to complete my seminar project and I ran into a bit of a problem. I'm quite new to the whole pspice related stuff and I'm avare that this problem might me fairly basic but I have no idea how to solve this.
    So the task was to get the schematic of Cable Amplifier using OPA660 from Texas Instruments website and then "test the ability to transfer digital dual-state signals of 0V and 1V levels and experimetally determin the highest possible transmission rate(bit rate) of the processed data." I'm quite sure that i have to basically change the imput source to 0-1V pulse, but the exact form somehow escapes me. The output should be a graph where the square wave gradually deforms but I just don't get how to achieve it exactly. So if anybody knows how to solve this please let me know, any help will be hugely apreciated and do not hesitate to ask for any further information to help you understand my problem assuming I didn't express everything clearly enough.
    Thanks Mark
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,370
    Think of your goal: to determine the highest transmission rate.

    Transmission rate is equivalent to frequency.

    So your input signal is a square wave of a known frequency.

    How is the squared wave degraded by your circuit?

    What happens when you increase the frequency of the square wave?
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    That type of test needs to done using the Transient Analysis function. Is that what you are using?
     
  4. Spoder

    Thread Starter New Member

    May 12, 2014
    6
    0
    Yeah thats it, I'm ought to find the certain frequency when the square wave starts to degrade but everything I tried ended up showing me not degrating square wave. This is what my netlist looks like after I changed up my source and analysis type.


    ***
    OPA660
    *
    R1 8 0 50
    R2 8 3 150
    Re 2 0 42
    RL 5 0 150
    Rq 4 1 250
    V 8 0 AC 1 PULSE(0 1 0 0 0 2.5u 5u)
    Vplus 7 0 5
    Vminus 0 4 5
    X1 1 2 3 4 5 0 7 5 OPA660X1
    *
    .lib OPA660X1.lib
    .tran 1u 50u
    .probe
    .end

    I think it should be solved using transient analysis but that just shows me time process.
     
  5. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    Is your transmission line model somewhat realistic?
     
  6. Spoder

    Thread Starter New Member

    May 12, 2014
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    It is, and the layout is supposed to be correct as well. The main problem might be that I'm not entirely sure what to put on Y axis of the graph.
     
  7. crutschow

    Expert

    Mar 14, 2008
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    You look at the input and output of the amp.
     
  8. Spoder

    Thread Starter New Member

    May 12, 2014
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    Meaning what exactly? Shall I use double Y axis and then print imput and output on it?
     
  9. crutschow

    Expert

    Mar 14, 2008
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    I'm not that familiar with Pspice, but yes, you plot the input and output (voltage probes) on the Y axis with time on the X axis. You don't need a double Y axis, you can print both on the same plot. What version of Pspice do you have?
     
  10. Spoder

    Thread Starter New Member

    May 12, 2014
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    The version I'm currently using is PSPICE AD Lite 16.6. Thanks for help I'll try that, but I think I already did that and didn't get exactly what I was looking for. the X axis should be frequency I think becouse I have to find certain frequency where the data is too deformed.
     
  11. Spoder

    Thread Starter New Member

    May 12, 2014
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    0
    Still no progress, I'm getting kinda frustrated here.
     
  12. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    Post your schematic.
     
  13. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    You cannot get what you want. You can only get time for the X axis, similar to an oscilloscope, using Transient Analysis, not frequency. You just increase the frequency of the square-wave (pulse) until significant distortion is noticed at the output. Then, from the time of the waveform period, you can calculate the frequency.

    You can get frequency on the X axis using the AC analysis mode but that uses only small signal sinewave analysis and you want square-waves. Those can only be generated in the Transient Analysis.
     
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