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INA500: what's the difference between differential layout of general purpose amplifier like TLV9062 and INA500?

Jim Chen (SEM)
Intellectual 2320 points
Part Number: INA500
Other Parts Discussed in Thread: TLV9062

Hi experts,

Could you help to clarify the difference between differential layout of general purpose amplifier like TLV9062 and INA500? Whether input impedance and CMRR of INA500 can improve sampling accuracy?

What are the advantages of the INA500 over TLV9062?

Would INA500 be more stable than differential sampling with TLV9062 for 50 Hz differential mode signals and 30 khz common mode signals?

Best Regards,

Jim

  • 0
    TI__Expert 8976 points

    Hi Jim,

    Great question. 

    Yes, a device like INA500 can offer significant benefit in system CMRR and gain error when compared to that of a discrete diff amp like TLV9062 with external resistors. 

    A spec of 87dB for the high CMRR region, and 77dB typical for the full rail to rail region may seem similar or worse when compared to other op amps, but it is important to remember that the INA500 is considering the internal resistors in this calculation:

    Resistor mismatch can very easily degrade system CMRR.

    Here is an app note which shows the mathematical calculation for system CMRR in a diff amp:

    Common-Mode Rejection Ratio in Difference Amplifier Circuits

    In the case of the app note example, we can see a worst case mismatch of about 40dB CMRR at DC when using 0.5% resistors (Poor performance irrespective of the amplifier)

    Compare that to the INA500 which has a worst case CMRR over the full input range of 62dB CMRR.

    Additionally, INA500 has exceptional accuracy compared to discrete diff amp designs: see typical gain error of just +-0.01% 

    By integrating the resistors on the same die as the amplifier, we are able to maintain accuracy which would otherwise require very expensive precision matched resistors, or a complex calibration scheme using a discrete device. Furthermore since all componentry is on one die, we tend to see that the over temp performance is improved as all internal components to INA500 experience a very low gradient of temperature. 

    Finally, errors associated with layout are effectively eliminated by integrating the resistors within INA500. This can also reduce system size and simplify layout by using an integrated device like INA500. 

    INA500 would offer better sensing accuracy and better common mode rejection characteristics in your proposed application when compared to that of TLV9062

     

    Please let me know if you have any other questions on INA500, I am happy to help support this design.

    Thanks,

    Jacob