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INA188: INA - Will Super-Balance topology improve offset drift?

Peter Baxter
Intellectual 420 points

Part Number: INA188
Other Parts Discussed in Thread: NE5532, OPA191, , INA592, THP210, ADS127L11

This could be an extension question to the following Forum Question.

"NE5532: Superbal circuit" - over 5 years ago.


Hi,

The circuit is part of a precision measuring instrument. Therefore I am interested in INA drift versus the (4) internal resistor(s) heat. 

Super-Balanced Diff Amp.png

Added to an Instrument Amplifier (INA188), is a Super-Balanced circuit (4 Opamp Instrumentation Amp). The 4th Opamp will be the OPA191.

With a 3 Opamp Instrument Amp circuit, there will be different power dissipated in each resistor string (R1+R2 versus R3+R4). In the 4 Opamp topology, the balancing makes the power dissipation in each string - the same.

Does the Super-Balancing improve/stabilise the offset drift due to "internal" resistor heating?

INA188 OPA191 AMP.TSC 

Will a precision circuit benefit from doing this? 

Thanks

Regards,

Peter Baxter

Might I be able to get an email address to send a simulation file - which is not public?

  • 0
    TI__Mastermind 29000 points

    Hi Peter,

    Just to clarify, you are now using the INA188 in place of the more discrete implementation? 

    Best Regards,

    Robert Clifton

  • 0
    Intellectual 420 points

    Hi Robert,

    I was originally using a MSOP8 4-Resistor package. Then moved to the INA592. Finally changed to the INA188. I'm going to use the OPA191 because of a recent forum question where Art Kay suggested that I use it (for another reason).

    Further to this, I have the FDA (THP210) ADC (ADS127L11). FDA's require a similar balanced 4 resistors. But around the resistors there needs to be an anti-alias filter. I ponder wouldn't it have been nice to have a precision resistor set inside FDAs. But its asking too much.

  • 0 in reply to Peter Baxter
    TI__Mastermind 29000 points

    Hi Peter,

    Thanks for clarifying. I'll move this post over to the right team that can help you with this. 

    Best Regards,

    Robert Clifton 

  • 0 in reply to Peter Baxter
    TI__Mastermind 27218 points

    Peter,

    Can you please restate and clarify your questions.  

    1. Draw the precise circuit you want to discuss with all the amplifiers, and components correctly identified.
    2. If temperature drift is a concern I need to know the specifications for any discrete resistors as well.  If it is a resistor network, let me know the model number.  If it is a discrete resistor, let me know the temperature drift (e.g. 25ppm/C).
    3. Restate your question and refer to your posted schematic in your question statement.

    Best regards, Art

  • 0 in reply to Art Kay
    Intellectual 420 points

    My apologies here.

    I re-looked at the Super-Balance circuit and my concept of what was happening inside was not correct. 

    Hence the question is irrelevant.

    Thanks for responding.

    Regards,

    Peter Baxter