Voltage Comparator in Multisim 10

Discussion in 'General Electronics Chat' started by yoppy, Mar 16, 2010.

  1. yoppy

    Thread Starter New Member

    Mar 16, 2010
    2
    0
    Hello,

    I'm trying simulate voltage comparator using Multisim 10.
    I use LM741 (as in "Circuit LM741.jpg"). The output is not limited to V+ or V-. Instead, it's going over kilovolt.
    Why? Can you explain to me?

    Then, I replace LM741 with 741 op-amp. The result is as expected (V+ or V-).

    What is the difference between LM741 and 741 ?

    Thx for helping .... [​IMG]
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Five bucks says it wont do that in practice. (for long)
     
  3. NatashaB

    New Member

    Feb 4, 2009
    2
    0
    Hi there,

    I think you have come across one of the simplified opamp models in the database. Some of the opamps have only 3-pins modeled (ie. inputs, and output - no power supplies). The models work properly in closed-loop configuration, but in open-loop (as seen here), they will not clip.

    Here's someone who had a similar issue on the Multisim forum: http://forums.ni.com/ni/board/message?board.id=370&message.id=6762&query.id=3269420#M6762

    My suggestion is to replace the model with one that has the power supplies modeled. There is a National Semiconductor model attached to the same component that has all pins modeled. To replace the model:

    1. Double-click on the component
    2. Click on Replace
    3. In the model field for the LM741H, select the National/LM741_3 model

    Let me know if you're still having trouble.
     
  4. yoppy

    Thread Starter New Member

    Mar 16, 2010
    2
    0

    Thank you so much... Your suggestion is very helpful. May be next time I will ask you again. may I know your email / YM ID? Mine is <snip>
     
    Last edited by a moderator: Mar 17, 2010
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