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What does a dB reference in voltage in LTSpice

Category: Software
Product Number: LTSpice
Software Version: XVII

I am used to the dB of a signal referencing the rms value of that signal, whether it be for power (50 ohm referenced) or voltage. However, it appears that LTSpice references the peak value.? For a transient analysis, I set the sinewave amplitude to 1V. When I plot this, I get a 1V peak waveform. If I switch to measure an AC analysis and set the AC amplitude to 1V, I see 0dB. That would seem to indicate that 0dB is referenced to a 1V peak signal instead of the rms or .707V. Is this correct for LTSpice?

Top Replies

  • AC_1V.asc

    This should make it clear, I hope.  To get a 1V rms sinewave for transient analysis (.tran), you would have to set the SINE voltage source amplitude to 1.414V.  The reason why the amplitude to…

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