perhaps an idiot question, but I can't find how to get an amplitude in dB, relative to time, in an analog graph. I search how to plot amplitude response of an audio envelope/shape generator in a lin and log fashion. Frequency and AC sweep graphs allow to choose linear or dB for Y scale, but others analog graphs don't allow this.
At the moment I use an home made "log convertor" to plot (in dBu) my audio signal amplitude - AD736 and trace with formula 20*log(P1/0.775). This "works" but I think there is a more elegant methode to achieve this.
Proteus plots standard Spice ANALOG ANALYSIS graphs in the time domain, and unfortunately Spice 3F5 cannot set directly amplitude for log scale. However there are a couple of ways you can do that.
1)
Use a AVCVS primitive (Voltage controlled voltage source) and set it with the formula to compute dB. You find it into the library at Modelling Primitives->Analog(SPICE). log10.pdsprj test shows it.
2)
Use of 'computed traces' in a graph. The log10_1.pdsprj shows how to do. The formula you can add with 'add trace...' are the same used for previous mentioned AVCVS primitive.
Thanks Ettore for this fast answer and your explanation.
Use of 'computed traces' in a graph was what I made before asking question, but use of AVCVS primitive is more simpler that my solution.
Just as a follow up of the matter, please find attached my method to get the envelope from a modulated signal in simulation.
This method is a 'surrogate' of the Hilbert's transform. It uses a different approach instead of a discrete convolution (inverse discrete FFT transform) but it ends up with a similar results: a (quasi) rectangular LP filter that removes carrier plus c+m and c-m components.
This approach is more performant in simulation than the your with AD736.
