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OPA189: Differential Bridge Amplification

Dennis McGlumphy
Expert 1390 points

Part Number: OPA189

I am using TI's TINA9-TI Spice simulation program.  I would like to perform a noise analysis on my circuit, please see attached file.  I have not found any information on how to set up a circuit for noise analysis.  If anyone has any information on this subject or can take my circuit and set it up for the analysis and explain what you are doing, I would be sincerely grateful.  Thank you.

Differential input-ouput with filter.TSC

  • 0
    Guru 48395 points

    First of all, you need an AC input source to run a noise sim, I could not find your R1, so I just put a source into the top of bridge and ran an output spot noise changing your meters to just a differential one across the final load - 

    Under analysis towards the bottom are the noise options, this one is output spot noise, pretty low noise actually. 

  • 0
    TI__Guru* 93105 points

    Hi Dennis,

    I looked over your OPA189 circuit. The TINA Noise Analysis function can be accessed from the "Analysis" tab near the top of the screen. Once you click on that tab you will see "Noise Analysis" near the bottom end of the list. That is the analysis you will need to select. It will ask you some set up questions for the noise analysis which you will need to provide answers.

    When I attempted to run the noise analysis an error message was received for your circuit, "Error - You must add an input to the schematic." Meaning there needs to be an ac generator added to the circuit so that frequency can be swept. Noise is determined and displayed as a function of frequency. I added a low-level ac generator in series with the dc circuit that biases the bridge. I also removed all of the VF points that were at a dc level so that just the OPA189 differential output noises were determined. You will find the results I obtained in the attached TINA file. You can set things up in it as you would like.

    Differential input-ouput with filter_01.TSC

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to Thomas Kuehl
    Guru 48395 points

    Oh, and I found the error giving very low noise in driving a single into the bridge. I needed to set a DC bias on that signal in the amplifier input range, changing that to be a DC 2.5V gave a more realistic output noise. 

  • 0 in reply to Michael Steffes
    Expert 1390 points

    Dear Mr. Steffes

    Thank you for your help.  Is there any documentation and/or examples on how to perform the available analyses in TINA9-TI?  Again, thank you for the help.  You can consider this issue closed.

  • 0 in reply to Thomas Kuehl
    Expert 1390 points

    Dear Mr. Kuehl

    Thank you for your help.  Is there any documentation and/or examples on how to perform the available analyses in TINA9-TI?  Again, thank you for the help.  You can consider this issue closed.