@User I also tried Murat solution which is simpler, and produces the same result. Be careful not to put the AC source in series with the inductor, since the inductor is open at any high frequency, and thus the ac source would be referenced to a floating net (the net attached to the inductor). You need to provide an AC ground to the signal source, i used a large capacitor as shown (ngspice does not complain about the dc-floating node on the large capacitor, since it uses GMIN conductances on all nodes to find the dc operating point).