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INA326: HOW TO SET OUTPUT WRT VREF/2 ON SINGLE SUPPLY.

vishal kakade22
Intellectual 355 points
Part Number: INA326

I am using INA326 to amplify signals from a load cell, Vdd=3.3V, I want to set output voltage wrt vdd/2,(considering load cell movement in both directions). In the datasheet suggested circuit is fig 2. But with this circuit, i am getting output voltage as 954mV.and according to figure 1, the output is exactly at vdd/2(which is correct), At balanced conditions. 

So, which is the correct circuit, fig 1 or fig 2?

  • 0
    TI__Guru 64840 points

    Vishal,

    The circuit in Fig 2 is the correct one for G=2,000 and it works as intended - see below. Check your connections or modify the schematic I attached in this post.

    INA326 Vishal.TSC

  • 0 in reply to Marek Lis
    Intellectual 355 points
    Hello Marek,

    Thank you for your reply, but as per your previous mail, does the Vref pin of INA326 should be driven by a low impedence source? or a simple voltage divider is fine?

    Thanks
    Vishal Kakade
  • 0 in reply to vishal kakade22
    TI__Guru 64840 points

    Vishal,

    For most traditional three op amps voltage feedback instrumentation amplifiers, they MUST have Vref driven by low impedance source or be grounded but INA326 is different.  Because of its current feedback topology, you either have to drive pin 5 with voltage divider for output referenced to Vcc/2 as discussed previously or connect R2 to ground - see below both cases.