A newbie and LTSpice

Discussion in 'The Projects Forum' started by manthura_assemblies, Feb 11, 2014.

  1. manthura_assemblies

    Thread Starter New Member

    Feb 11, 2014
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    0
    Hi everyone,

    I was playing with LTSpice, trying building a simple integrator circuit. I have used the opamp labeled as Opamp2 in the components folder [Opamps].

    The problem is that when I tryto to launch simulation, a popup appears saying 'Unknown subcircuit called in: xu1 0 n001 vp10 vm10 out opamp2'.

    Maybe is there a problem with subcircuits with voltage sources?

    I have attached the .asc file.

    Thank you very much for your support.
     
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,504
    380
    hi,
    Is there any reason that you cannot include an OPA from the pop up box [ F2] listing.?

    E

    EDIT:

    Look for this asc file under the Educational examples in the LTS folder. opamp.asc

    It explains how to add your parameters to the opamp model.
     
    Last edited: Feb 11, 2014
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    All better now.

    Several issues: OpAmp2 is a symbol only to be used with a user-supplied model. There is no automatic underlying simulation model. OTOH, UniversalOpAmp is a "generic" opamp symbol with a parameterized simulation model where you can set various attributes, like open loop gain, slew rate, bandwidth, etc. If you wanted to simulate with an LM358 opamp, for example, you would start with OpAmp2, use the attribute editor to change the value attribute from opamp2 to LM358. Then you would use the .LIB or .INC directive to point to the file that actually contains the sim model for the LM358. Or as Eric points out, you could select from one of dozens of simulatable opamps supplied by LTC.

    If you simulate without either specifying STARTUP in the .TRAN statement, or setting the initial condition (.IC directive) on node out. During the initial dc bias solution, before the transient simulation runs, node out is set to -10V. To actually see the integrator in action, you have to override the value found by the bias solution. An alternative is to suppress the initial bias solution by adding the STARTUP directive to the .TRAN statement.
     
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    Last edited: Feb 11, 2014
  4. manthura_assemblies

    Thread Starter New Member

    Feb 11, 2014
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    0
    MikeML, thank you very much for your clear and concise explanations. I'll go studying the directives more deeply.
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
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