My problem is that I want to simulate a circuit with a transient analysis but as soon as I hit the simulate button, the simulation runs and runs and runs and won't terminate (although my stop-time is already at 0.1 s). Since I don't have much experience in SPICE, I think my problem lies in the embedding of external 2 op amps. Therefore I followed these steps (correct me, if I did something wrong here):

  1. I searched for the .cir files of the mentioned op amps and saved the files in the same directory, my schematic is located.
  2. I looked for the name after .SUBCKT in the .cir files and auto-generated a fitting symbol. After placing it in the circuit, I renamed the value and set the prefix to X.
  3. I used .include <filename>.cir to include the .cir file

After that I built my circuit and hit the simulation button. Anyone knows where my problem might be?

edit: Here are my circuits. I embedded the two op amps (there isn't any mistake in the pin connection) Circuit which I want to simulate Schematic on LTspice

  • 1
    \$\begingroup\$ Can you add a picture showing the circuit? \$\endgroup\$ Aug 3 '16 at 13:11
  • 2
    \$\begingroup\$ Depending on what you're simulating, 0.1s can be a long time. \$\endgroup\$
    – W5VO
    Aug 3 '16 at 13:18
  • \$\begingroup\$ I added two pictures. I hope they will help :) \$\endgroup\$
    – Tobbe
    Aug 3 '16 at 14:15
  • 1
    \$\begingroup\$ Are you sure you want to run your AD8221 without a power supply? \$\endgroup\$
    – pipe
    Aug 3 '16 at 15:04
  • \$\begingroup\$ I found my problem: It was the low performance of the main cpu... ~~ and I spent 2 hours on that problem \$\endgroup\$
    – Tobbe
    Aug 3 '16 at 15:39

Your stop time is 0.5 s according to the .tran statement on the schematics. This is a very very long time for a transient simulation of this type. I suggest you set the stop time to f.ex. 10 ms giving 4 periods of the 400 Hz sinus you are using as excitation.

The first Opamp probably works better if you connect it to a power supply. At the moment I would not expect it to output anything. This is something that is normally omitted in a principal schematics like the one on top. This is done to improve readability. But you still have to connect it to make the circuit work. Both in simulation and in the real world.

  • \$\begingroup\$ It's an instrumentation amp, not an op amp \$\endgroup\$ Aug 9 '16 at 11:01

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