(Solved) AC Simulation - What am I doing wrong?

Schematic Simulation (Ngspice)
1

V7.0.8.

I have a small project (attached), just a simple LP filter.
It simulates beautifully in “Transient” mode, showing how my output sine voltage decreases when increasing the frequency of the V1 sine source.
Great! Now’s the time to make some nice amplitude/phase plots over frequency.
Choosing “AC”, 100 points/decade, start 1 Hz, end 10 kHz, I end up with two perfect horizontal lines, one at 0 dBV, the other at 0 degrees.
Not quite what I expected…
So what an I doing wrong? There must be a simple explanation, but I’m apparently too dense.
I could imagine that Ngspice needs some kind of directive to know it shaould do the frequency sweep on V1, but I find no such option/command anywhere.

Thanks.

Scratch2.zip (13.7 KB)

Measuring point in all cases: the opamp output.

2

I have never even tried to simulate anything with KiCad and don’t have KiCad here.
As I remember from PSpice (I was last time using many years ago) to do the AC simulation I had to specify the AC voltage for V1 (I typically used 1V). May be you have 0V AC at V1.

3

No.
V1 is working, otherwise transient simulation wouldn’t work.

4

Problem solved. My V1 source was missing the “ac=1” parameter.
Sorry for wasting time.
Cheers.

5

Waveform specified for transient can’t be used for AC.