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OPA320: OPA320

Jiachen Li
Prodigy 10 points
Part Number: OPA320


When we use this to transfer differential to single, we need a REF as shown below. My question is can we use a divider to generate this REF voltage? Does the Amp have some influences to divider voltage?

  • 0
    TI__Guru 69431 points

    Jiachen,

    Because the REF pin must be able to sink/source current, this would disturb your voltage divider and thus REF pin must be driven by a low impedance source. For that reason, you may NOT use voltage divider as shown in your schematic unless you buffer it with another op amp in gain of 1 - see below.

  • 0
    TI__Expert 5850 points

    Hello Jiachen,

    I would highly recommend using an op amp in a buffer configuration between the voltage divider and the REF node going into R25.  This will minimize loading effects that will affect the transfer function of the difference amplifier.  It is not recommended, because you will have to tailor the resistance values of the voltage divider and R25 to match the value of the feedback resistance (R27+R31) within the transfer function to have a balanced difference amplifier.  This would be rather difficult due to component tolerance.  I have derived the transfer function and attached it to this thread post for schematic in the initial post. 

    OPA320 Difference Amp.pdf

    Best regards,

    Errol Leon

    Texas Instruments 

    Precision Op Amp Applications