I have a question about the dB scale in Ltspice. As far as I know it uses 1 of the unit (so 1V in case of Voltage) as a reference and then plots the dB value, which is defined by 20*log(V/Vref). (So the lower image is the voltage of my circuit with the y axis property set to dB.)
But when I plot this exact formula in LTspice the plot is actually mirrored at the x-Axis. (Upper plot) Why is that? I think it should be the same. What is my mistake?
Hope you can help!
Edit: I plottet abs(V(n009)) since the phase is not important for my application and just gives a messy plot. I also have the same problem with any schematic, so I guess the problem has nothing to do with the circuit.
For clarification: easy schematic, same problem (this time it's the current).
Best Answer
It's not an LTspice problem, it's the way the waveforms are displayed: magnitude, instead of amplitude. If you plot
sin(w)
, you won't see asin(x)
waveform, but anabs(sin(x))
. The difference will be in the phase: in your plots, the phase appears centered around180
degrees for the formula, while the "normal" plot shows it's centered around0
. That's why exporting the waveform will make them "look" fine -- it's a matter of appearance.