TI Instrumentation AMP Model

Discussion in 'General Electronics Chat' started by Management, Feb 22, 2008.

  1. Management

    Thread Starter Active Member

    Sep 18, 2007
    How is everyone doing? Quick question.

    I downloaded TI's Instrumentation Amp model for a Part # INA121.

    You can see it here: http://focus.ti.com/docs/prod/folders/print/ina121.html

    I first make the library and symbols using model editor. When I go to a schematic and select the library, I see 4 different symbols. It looks like 3 of them are opamps and one is the device but the latter's pins don't match up.

    My question is, why can't I get the one symbol that they have pictured in the datasheet? Why am I getting 4 and how do I use it to model the actual device? Do I just have to make the device from what is pictured in the datasheet?

    I'm sorry if this is a silly question but I have never ran into this before.

    Thank you.

  2. Management

    Thread Starter Active Member

    Sep 18, 2007
    Maybe I think I got it. Probably they give you the option of designing your own Intru. AMP but the other one is the whole thing. Just the pins do not match up. I hate that.
  3. scubasteve_911

    Senior Member

    Dec 27, 2007
    I'm a bit confused by your question. What software are you using first of all? Secondly, are you trying to use the SPICE model given by TI?

    If you're using the SPICE model from TI, then it is incorporating several opamps to implement the overall instrumentation amplifier. As you are probably aware, the instrumentation amplifier is two non-inverting amplifiers fed into a differential amp, along with gain-setting parts, etc. You are likely seeing these individual components, which makes me think that you aren't invoking the model correctly from your symbol representation.

  4. nanovate

    Distinguished Member

    May 7, 2007
    This is the first line of the model file for the INA121:
    * INA121 = A1_121 + A2_121 + A3_121 OP AMPS + PRECISION RESISTOR NETWORK

    You want to select one corresponding to --> .SUBCKT INA121