Setting the Saturation V_ce and V_be in LTSpice

Discussion in 'Programmer's Corner' started by Rainier Azucena, Mar 8, 2016.

  1. Rainier Azucena

    Thread Starter New Member

    Dec 18, 2015
    I've been doing a few test with BJTs. A lot of times it's just easier to see how the general ideas pan out, so turning of a few nuisances and idealizing everything is great. But I can't seem to find a direct way to set both Saturation V_ce and V_be of NPN to 0V. How do I do it? It's not explicitly defined so does it only arise from the other parameters?
  2. ScottWang


    Aug 23, 2012
    Please attach a file as circuit.jpg for your circuit with 800*600 and the LTspice file as circuit.asc.
  3. crutschow


    Mar 14, 2008
    It is defined by other BJT parameters, but I don't think you can readily adjust them to make Vce and Vbe equal to zero.
    If you really want to simulate an ideal BJT (and I see no good reason to do that) then you can use the current-dependent current-source (f) located in the component selection window.
    Read the Help file on it to determine how to set the parameters for the desired operation.
  4. WBahn


    Mar 31, 2012
    I think most device models are moving to parameterized models instead of physics-based models -- this means that the device behavior is defined via polynomial curve fitting to actual data. This is certainly true for process models, but I imagine that a lot of existing discrete models are still physics-based just because there's no compelling reason to change. But even with the physics-based models the Vce and Vbe voltages are derived. They are NOT constants -- that would almost completely defeat the whole point of the simulator!