I am new in this forum and doing my first steps with the ngspice simulator built into Kicad 5.1.5.
Unfortunately, despite having already invested many hours, read tutorials, run examples, I couldn’t get a meaningful simulation result with a very simple LMV358 circuit.
My circuit is the the well known Sallen-Key 2nd order low-pass filter. I enclose the project:
sallen_key_LMV358.zip (5.8 KB)
I obtained the LMV358 model (see enclosed LMV358.MOD) from T.I. and know that it is correct (it works with the Tina TI simulator).
Then, according to the tutorial, in EEschema I matched the pin sequence of the SPICE model with that of the schematic symbol using the “Alternate pin sequence” field in the SPICE model property dialog. The following screenshot:
Simulation runs without errors, but the simulation results (e.g. AC sweep Bode plots) are completely wrong: see here: . The amplitude frequency response (red trace) looks rather like that of a high-pass.
And very oddly, the only way to obtain a frequency response that looks more or less like a low-pass, is to leave the VSS pin of the LMV358 floating!
A few more strange things that I noticed are:
After having entered the Alternate pin sequence in the SPICE model properties of the LMV358 (which in my case would be: 1 2 3 4 5), saved and closed the dialog, the strange thing is that I find the Alternate pin sequence field empty if I return to the same dialog again at a later time.
This does however not happen if I use commas as separators in the Alternate pin sequence: 1,2,3,4,5. But according to the tutorial, the correct separator is the blank space, not the comma. Isn’t it?
Entering an Alternate pin sequence seems to have no effect at all to the simulation results. Results are always the same (wrong ones). Even if I enter explicitly wrong pin sequences.
I would be so thankful if anyone can help me getting started. At this point I’m completely lost!