open-source-silicon.dev

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Hi <@U01819B63HP> I'm trying to generate this curve using Xschem and ngspice but I couldn't find a way to plot the frequency

also the phase noise versus the offset frequency

<@U01UTPXQ2NQ> .ac is used to vary the frequency and plot frequency response as far as I know. Is there another usage of it ?

You have Fout and Vcont. Is this not what you want? Frequency depending on Vcont? Probably you can sweep Vcont?

<@U01UTPXQ2NQ> I thinks he wants to plot the oscillating frequency of a VCO as simulated in a transient analysis, vs the controlling VCO voltage.

Oh okay. Then I do not have an answer to that. If I was trying probably will use the python to collect and analyze the data of multiple simulations done with .control .endc

<@U01UTPXQ2NQ> <@U03RSL4SJ4S> yes i think the easiest way is to masure the period and print the result using a `.measure` instruction, sweep multiple Vout points and then plot the results using any available tools (gnuplot/excel/python or may be ngspice itself, you can create new ngspice vectors and plot them).

test_vco.sch

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<@U03RSL4SJ4S> following example does the Frequency vs Vcont plot, i used a simple current controlled ring oscillator, only to test the plot.
The ngspice commands can be optimized, i am sure, but you can start from this example.
To see the graph in xschem update your xschem installation (`git pull &amp;&amp; [sudo] make install`) since ngspice creates a different Plotname when saving custom created vectors.