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INA128 output problem

Ng Shao Kay
Prodigy 10 points
Other Parts Discussed in Thread: INA128

Hi all,

I am currently using this ic in my mini project, but i encounter problem in its output.

I connect the ic as shown in figure below. Then the connection of V+ = 3V from battery, V- = ground from battery, Ref = ground from battery. I left the Vin- and Vin+ open. When i change the Rg value from 1k to 100 ohm, the output Vo doesn't change. Vo maintains at about 1.6 V  even though Rg has been changed. Suppose the Vo will change when Rg change. I wonder where the problem occurs.

Thanks.

  • 0
    TI__Genius 15410 points

    Hi Ng Shao Kay,

    The INA128 requires a minimum supply voltage of +/-2.25V, this means with a single supply the device requires +4.5V. Try connecting V+ between +4.5V and +36V and V- to ground.

    Also,the input pins can't float, they must provide a current path for the input bias current, otherwise the input amplifiers will saturate.

    To get a proper output, the device must be supplied with a common mode voltage. Please see the figures titled INPUT COMMON-MODE RANGE vs OUTPUT VOLTAGE.


    Thank you,

    Tim Claycomb