Problem with Waveform displaying DB() and PH() for signals of below -100dB
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andyfierman 4 years ago
**BUG** Concise problem statement: Please see: https://easyeda.com/andyfierman/Problem_with_Waveform_displaying_DB_and_PH_for_signals_of_below_100dB-DQ20mk3pL Steps to reproduce bug: 1. Run sim in link above. Results: Errors in DB() and PH() plots. Expected results: DB() and PH() plots. plots should look like they do in this sim: > http://www.ngspice.com/index.php?public_circuit=qiAlMw but with correct Y axis labels of `dB` for dB magnitude plot and `degrees` for phase plot. Browser:
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andyfierman 3 years ago
In: https://easyeda.com/editor#id=74417e663ea44e65bde9407c090a5aad there are two problems. 1) When plotting DB(V(out)) and PH((V(out)) from a Volprobe, the Y axes are labelled correctly with dB and degrees but the traces show significant errors as the DB plot approaches -100dB attenuation. Both the attenuation and the phase are incorrect; 2) If instead of using DB(V(out)) and PH((V(out)) or `probe V(out)` these forms of expression are used: `probe 20*log10(MAG(V(OUT))) PH(v(out))*360/(2*pi)` or probe DB(V(out)) PH(V(out))*360/(2*pi) then the traces are plotted correctly but the Y axes are labelled in `V` instead of the dB and degrees. * In email conversation with Leigh Marble about these problems, he suggested that to avoid ambiguity when using the different expressions to plot dB and phase, it would be better to simply remove the units form the dB and the phase plots. Then when plotting both dB and phase, using any expression, the scales would be correct, there just would be no units shown. (In fact this makes sense in the dB scale since dBs are unitless anyway.) * This may also help to fix the plot errors at -100dB and below.
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