Edge triggered DFF

Discussion in 'Homework Help' started by Faizan Ahmad, Mar 26, 2016.

  1. Faizan Ahmad

    Thread Starter New Member

    Mar 6, 2016
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    I want to make an edge triggered DFF using LTspice.
    Tried to build a latch , I am getting spikes at the output.
    If somebody could help me with that.

    attaching the file
     
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  2. WBahn

    Moderator

    Mar 31, 2012
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    If you would, take a screen shot of your circuit schematic, save it as a reasonably sized PNG file, and post it. That will allow more people to look it over. You might also post your sim results showing the spikes you are talking about.
     
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  3. Faizan Ahmad

    Thread Starter New Member

    Mar 6, 2016
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  4. WBahn

    Moderator

    Mar 31, 2012
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    It's likely that the cause of the spikes is charge injection due to too fast rise and fall times combined with using an ideal pulse source that can source/sink unlimited current.

    Take your two pulse sources and run them through inverters (or a pair of inverters if you don't want to deal with the signal inversion) similar to how you derived clkb. That will give you realistic rise and fall times and drive strengths.
     
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  5. Faizan Ahmad

    Thread Starter New Member

    Mar 6, 2016
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    20160326185711.jpg


    Thanks the spikes are gone.

    next is this what I want to do , I copied the circuit to make a slave ckt. , Is that right
     
  6. WBahn

    Moderator

    Mar 31, 2012
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    Depends on what you are looking to achieve. Do you want the data to be edge-sensitive on one edge but the output to change on the other edge? Or do you want the output to change on the same edge?
     
  7. Faizan Ahmad

    Thread Starter New Member

    Mar 6, 2016
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    I want the output to change on the same edge
     
  8. WBahn

    Moderator

    Mar 31, 2012
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    So look at the proposed circuit and ask yourself if that is even possible.
     
  9. Bordodynov

    Active Member

    May 20, 2015
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    Spike appear due to the fact that the parasitic capacitance does not take into account the source and drain. You can simply get rid of the spike using in Scheme following: .option cshunt=1f.
    This will add the specific capacity to each point of the circuit.
     
  10. Faizan Ahmad

    Thread Starter New Member

    Mar 6, 2016
    9
    0
    thanks to all
     
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