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Spice: Can it display Watts or dBm?

Discussion in 'Electronic Basics' started by billcalley, Aug 24, 2007.

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  1. billcalley

    billcalley Guest

    Hi All,

    I would like Spice to display results in Watts or dBm. Is this even
    possible? Spice only seems to want to graph voltages or currents --
    and in the FFT portion it only seems to show dB. (I'm using LT
    Spice).

    Thanks for any help!

    -Bill
     
  2. D from BC

    D from BC Guest

    I believe it's the Alt key for I*V power.

    D from BC
     
  3. billcalley

    billcalley Guest


    Hi D from BC,

    I should have been far more specific! I meant force Spice to graph
    the RF output signal in Watts or dBm; and more specifically during a
    frequency domain FFT output.

    Thanks,

    -Bill
     
  4. Tom Bruhns

    Tom Bruhns Guest

    Sure it's possible. Try this:
    1. Run your simulation, and display the voltage across a resistor and
    the current through that resistor.
    2. Right click in the graphics window; select FFT; select both the
    current and the voltage to display as FFT (so that the FFT will be
    calculated for both).
    3. In the FFT window, right click the voltage trace label at the
    top. Change the expression to the voltage times the current.
    4. Right-click in the left margin of the FFT graphic; change to a
    linear display.

    Presto, you should see watts displayed.

    Cheers,
    Tom
     
  5. billcalley

    billcalley Guest

    Thanks Tom -- works like a charm!!

    Best Regards,

    -Bill
     
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