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OPA313: current sensing circuit Vref

Part Number: OPA313

Hi there.

The attachements are given by TI's engineer's cookbook : Amplifier (p57, Low-side, bidirectional current sensing circuit).

I don't exactly understand why Vref is needed.

It's relevant with the issue of my customer. My customer connect the Vref to the GND, I wonder it might cause the issue.

Thank you for your promp attention!

  • Hello,

    Vref is used to bias up the output voltage to mid supply. If Vref is equal to ground then the output voltage will try to swing negative during negative load currents. If you customer has bidirectional load currents and they are using a single supply for the amplifier they must provide some sort of reference voltage. 

    Take a look at the transfer function of the circuit provided under Design Step 1 on page 58. If the load current (Ii) is negative the output voltage will be negative if Vref is 0.

    Thank you,

    Tim Claycomb