Tool/software:
Hello,
I am trying to run a stability simulation in LTspice for the OPA354 differential amplifier, following the method shown in TI’s training presentations. The goal is to extract the phase margin by plotting Aol, 1/β, and loop gain.
Here are the details:
-
Setup:
-
LTspice stability testbench for OPA354 in differential configuration.
-
Measurement of Aol, 1/β, and loop gain as in TI training examples.
-
-
Expectation:
-
Aol should resemble the open-loop gain curve from the datasheet (≈120 dB at low frequency).
-
Aol and 1/β should intersect at some frequency to allow phase margin analysis.
-
-
Actual result:
-
Simulated Aol is about –16 dB (much lower than expected).
-
Because Aol is so low, it never intersects with the 1/β curve at any frequency.
-
If I replace only the op amp model (e.g., with OP777), the simulation looks correct and behaves as expected.
-
-
Question / Request:
-
Why does the OPA354 model produce such a low (and incorrect) AOL in this LTspice setup?
-
Is there something specific about the OPA354 macromodel or setup that I need to adjust?
-
Could you please correct what is wrong and provide me with a working simulation example where the phase margin (PM) can be clearly extracted?
-
I have also attached my LTspice simulation files (schematic and models) so you can reproduce the issue.
Thanks in advance,
Idan
