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LTSpice: Complex numbers?

Discussion in 'Electronic Design' started by Joerg, Jun 7, 2013.

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  1. Joerg

    Joerg Guest


    Is there a way to coax LTSpice to display complex numbers in the form of
    x+jY (or x-jy if leading phase)?
  2. Joerg

    Joerg Guest

    So I asked this question on the Yahoo group (after finally getting past
    this dreaded captcha stuff), and the LTSpice-guru Helmut Sennewald had
    the answer:


    Make the waveform window active.
    Left click on any number of the left vertical axis.
    Then select Cartesian instead of Bode or Nyquist.
    Representation: "Cartesian"
    When you now select a signal, LTspice will show the numbers
    for the real and imaginary part.


    I had found that on the web yesterday but gave up because it did not
    work. Turns out it does not work in a transient analysis but it does in
    an AC analysis.
  3. Joerg

    Joerg Guest

    It shows them as:


    A bit unorthodox but good enough for me. The nice thing is you can make
    them visible just by hovering over the spot of interest in the waveform
    window. I need this to corroborate the numbers my software will calculate.

    Full confession: This stuff has been so long ago that I needed to brush
    up. And right now I am getting a complex impedance where there should
    only be a capacitance (sans real component). Hurumph!
  4. Joerg

    Joerg Guest

    Same here, but you know how it goes. Wet finger in the air, black cat
    crosses street, "Oh, need another 3nH here and 4pf over yonder", throw
    onto SPICE, find it's really 4nH and 5pF, put that in the design, done.

    I have to extract the capacitance from a ref/sense ratio measurement and
    through a lossy LC network. No fun. One of our guys had a billiant idea:
    Give it to a college kid, let him/her solve it and pay $50 or whatever
    is fair for it. But that feels like cheating :)
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