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How to use vcvs as an OR or AND gate

sohaiba

Please can you elaborate how to use the vcvs source as OR or AND gate? How to connect the terminals?

  • Andrew Beckett

    Use vcvsp (not vcvs) from analogLib. That allows you to specify the number of controlling voltages (i.e number of inputs to your logic gate). Then specify the type of source as "and" or "or" or whatever you want. 

    See the attached picture with a schematic (showing the property assistant to see the properties on the vcvsp), and the resulting waveforms.

    Regards,

    Andrew.

  • surreyian
    I tried to configure a NAND/NOR gate with the example given, but NAND/NOR gates gave the same result as AND/OR gate. Any other setting required?
  • Andrew Beckett

    Yes, it's a bit of an oddity - but one that comes from the same feature in certain other SPICE simulators - they also behave the same way where AND and NAND are equivalent (I just checked). This isn't entirely surprising if you think about it, because there's no information on what the inversion would be...

    To get the inversion, you have to set the "Type of transfer char" to PWL, and then you can specify a PWL mapping of input to output voltage (so for example, in my case if I have 4 inputs in the PWL vector, with inputs 0, 0.2, 1.8, 2 and outputs 2, 1.8, 0.2, 0 - this will achieve the inversion (I had a 2 volt "supply" in my case).

    Regards,

    Andrew.

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