I have moderate experience with LTspice and thought it would be nice to try the integrated simulator in KiCad so I don’t have to re-create circuits. I tried a simple hello world example for a non-converting amplifier using a common TLV333 (sometimes known as OPA333) model downloaded from Texas Instruments. When I did the .dc sweep of a 0-1V signal into the OPAMP- pin, I saw the Voutput (in red) had some weird glitches or dips which made the output behave accordingly. I noticed Vinput / Vop+ (in yellow, drawn in since I forgot to show it) was normal, however the Vop- pin had similar glitches.
- I did a sanity check with a .op simulation at those swept voltages, and indeed it was so.
- I replaced with the built in op-amp model and did not recreate the issue.
- I exported to a .cir file and simulated in LTSpice program and did not recreate.
- I changed the load resistor to 10k and the issue went away.
I can see that the load is affecting the performance of the circuit. I just can’t understand why that would create such weird dips at specific voltages.
Edit: posted file!
test-sim-kica.zip (71.1 KB)