I couldn't find anything about " Error Report" in LTspice too. Besides I found nothing on numerical limitations. It seems no one has this kind of problem. I would keep searching, hope to find something related to this issue.
In all around different websites they said: " email bug reports to LT
spice@linear.com"
Hi,
Actually it is the Spice Error Log. I checked it though and all it seems to indicate is that it has trouble finding the operating point.
It works faster with ".option noopiter" anyway so i tried that but it did not solve the problem where the LM358 does not act as an amplifier anymore.
As a simple experiment, i gave the right hand circuit its own plus and minus 15v supply, and gave it its own input sine source. I then changed he left hand side circuit sources to 0v. One of the LM358 op amps then started to work normally again.
So when some of the components are taken out of the circuit, even if that circuit is not connected to the circuit being tested, the spice program starts to show the correct results again. That must mean there are limitations that we cant see just yet.
To test this yourself just view the output of one of the LM358's with a node label. Give each circuit its own supplies and input source. Ground each side supplies in turn while you test the other side, and test without grounding any supply voltages. Big difference between grounding one circuit and not grounding one circuit, when there should be no difference at all (testing only one circuit op amp output, that's all).
There is a workaround but it's not easy. Curve fit the CM output and then use the resulting function in the graph display entering that function instead of the usual V(cm).
So say we use a second order curve fit, we'd end up with something like:
vcm=A*f^2+B*f+C
so instead of using:
V(diff)/V(cm)
we'd use:
V(diff)/(A*f^2+B*f+C)
Alternately just do three points and do the extra math by hand (ground out one side at a time to get the diff and cm):
diff1/cm1
diff2/cm2
diff3/cm3
That would probably be good enough for most purposes. Not an entire graph of CMRR vs frequency, but probably good enough to get an idea what is going on.