[Error]Too many iterations without convergence

[kazu098]

Hi, I’m Kazu.
I’m new to Kicad.
I created and simulated a circuit for EEG detection and got the following error.

doAnalyses: Too many iterations without convergence
run simulation(s) aborted

The EEG circuit is a combination of an instrumentation amplifier, a Sallen-key low pass filter, and a 50hz notch filter.
AC analysis and transient analysis work fine when testing each above individual circuit, but when I combine the circuits, I get the above error. I would appreciate it if you could tell me the cause of this problem.

I would like to attach the Kicad file, but since I’m a newcomer to this forum and can’t seem to attach files.

Thanks in advance.

eeg_circuit.zip (25.9 KB)

[hermit]

@kazu098

I would like to attach the Kicad file, but since I’m a newcomer to this forum and can’t seem to attach files.

Fixed. You should be able to attache now.
Welcome aboard.

[kazu098]

Thank you very much!
I could attach the Kicad file

[ML9104]

You may have to look at he integrator in the differential amp loop. Integrators need a start condition, eg, by shorting the cap.

[holger]

A way to bypass the starting conditions for transient simulation is using
.tran 200u 2 1 uic
This starts with 0 voltage, if not specified otherwise, and the first second is skipped until the signal is stable.
For ac we still will need a stable operating point though

[kazu098]

I could display the transient simulation following your advice.
Thank you very much.