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Non-linear model for SPICE

Discussion in 'CAD' started by wombat, Jul 14, 2006.

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  1. wombat

    wombat Guest

    Hi All,

    I need to create a resistor whose resistance varies according to an
    equation with the variables of the top and bottom voltage (ie. the
    voltage across it). I use Altium (was Protel) but I suspect the
    fundamental process is the same. My main concern is that it is what
    excel would refer to as a circular reference but I don't understand the
    inner workings of SPICE tools to know whether it's feasible.

    Cheers,
    wombat
     
  2. Jim Thompson

    Jim Thompson Guest

    In PSpice this is done with behavioral models, for example "GVALUE",
    which is a current source written as an equation relating to the end
    voltages.

    In other Spice's I believe these are called "B" sources.

    ...Jim Thompson
     
  3. In generic spice you use the "B Source".

    e.g

    b1 1 0 i=2.4*V(1,0) + 3.5*V(1,0)*V(1,0)*

    This makes the current through nodes 1,0 be a function of the voltage
    across it, i.e. a non-linear resister.

    You should make a .subckt model with all the details in it etc...read
    manual etc..

    Kevin Aylward B.Sc.

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.

    "There are none more ignorant and useless,than they that seek answers
    on their knees, with their eyes closed"
     
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