[Multisim] Transient time point calculation did not converge

Discussion in 'General Electronics Chat' started by xxxyyyba, Sep 26, 2015.

  1. xxxyyyba

    Thread Starter Active Member

    Aug 7, 2012
    283
    6
    Hi. I have problem simulating this circuit in Multisim:

    (LTSpice)

    sema.png

    Here is scheme from Multisim:

    multi.png

    When I run transient analysis, I got this:



    ------ Checking SPICE netlist for Design3 - Saturday, September 26, 2015, 10:58:03 AM ------
    ======= SPICE Netlist check completed, 0 error(s), 0 warning(s) =======
    Transient time point calculation did not converge
    Simulation canceled



    Any idea what's wrong? Thanks in advance
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    7,101
    1,481
    Do you need to connect the unused pins of the IC to something?
     
  3. xxxyyyba

    Thread Starter Active Member

    Aug 7, 2012
    283
    6
    I don't think I need...
     
  4. xxxyyyba

    Thread Starter Active Member

    Aug 7, 2012
    283
    6
    I tried different models of opamp and I got same error. Here is my version of software:

    [​IMG]
     
  5. xxxyyyba

    Thread Starter Active Member

    Aug 7, 2012
    283
    6
    And with previous version I didn't have problems simulating circuits with opamps. I think this problem has something with opamp power supplies, if I remove them, simulation starts without error. But opamp must have power supply to work :)
     
    Last edited: Sep 26, 2015
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    7,101
    1,481
    Maybe your new software version is more picky about unconnected pins? Wouldn't hurt to add the offset null pot and compensation cap as per the datasheet. Convergence problems often need only a trivial adjustment of a circuit parameter to overcome them.
     
    xxxyyyba likes this.
  7. xxxyyyba

    Thread Starter Active Member

    Aug 7, 2012
    283
    6
    Thanks for suggestions, I will firstly install older version in virtual OS to see if I can simulate same circuit.
     
  8. xxxyyyba

    Thread Starter Active Member

    Aug 7, 2012
    283
    6
    I get same error on Multisim 13.0.1 Power Pro. There is something wrong with this model of op amp in both versions of Multisim I tried. :confused:
     
  9. Jony130

    AAC Fanatic!

    Feb 17, 2009
    4,174
    1,188
    Can you upload Multisim 13 simulation file?
     
    xxxyyyba likes this.
  10. xxxyyyba

    Thread Starter Active Member

    Aug 7, 2012
    283
    6
  11. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,333
    Usually convergence issues are caused by shorts (I think?). Try adding small resistors (1 milliohm) in series with the power supplies. If I remember right, Multisim does not like "backwards" power supplies (used for the negative voltage supply).
     
    xxxyyyba likes this.
  12. Jony130

    AAC Fanatic!

    Feb 17, 2009
    4,174
    1,188
    LOL You connect your op amp power supply backwards. Pin 4 is V- and pin 7 is V+
     
    DerStrom8 and xxxyyyba like this.
  13. xxxyyyba

    Thread Starter Active Member

    Aug 7, 2012
    283
    6
    @DerStrom8,
    I added 1 miliohm resistors in series with opamp power supplies and simulation starts without error. However, output voltage waveform doesn't look as it should. But I think we are close to solution :)
     
  14. xxxyyyba

    Thread Starter Active Member

    Aug 7, 2012
    283
    6
    @Jony130,
    I made really stupid mistake :)
    Thanks a lot!
     
  15. Jony130

    AAC Fanatic!

    Feb 17, 2009
    4,174
    1,188
    But why you simply do not use a LTspice? I think that LTspice is the best software for analog circuit simulation.
     
  16. xxxyyyba

    Thread Starter Active Member

    Aug 7, 2012
    283
    6
    Well I'm not familiar with LTSpice yet but I definitely need to start using it.
     
Loading...