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INA326 output saturation

Salvatore Aiello
Prodigy 10 points
Other Parts Discussed in Thread: INA326, INA333

Hi,

Testing the INA326 on a breadboard. Circuit as below. Output offset 100mV. Intend using for transducer voltage translation with user adjustable gain. Everything working as expected except that on occasion ( about 20% of time ) when powering up, the output will hit the supply rail. Disconnecting and reconnecting the supply usually resets the circuit to normal. What is happening here?  How can I resolve this issue? Any help appreciated, thanks.

  • 0
    TI__Mastermind 25815 points

    Hello Salvatore,

    I would like to caution the use of potentiometers and breadboards when evaluating this device for the gain-setting pins are sensitive to parasitic capacitances due to its unique topology.  The device will performed the best when placed on a PCB with a fixed gain-setting resistor.  Be sure to place the gain-setting resistor as close to the device as possible so as to minimize stray capacitances. 

    In addition to the potentiometer caution, here are some things to look at:

    a)      Use a scope to examine the inputs, output, and power rail during power up

    b)      Perhaps you have a bad or noisy potentiometer at the input or even at the gain-setting pins.  It is recommended that you ensure they are clean and do not have an open circuit on the wiper.  You may also want to place a capacitor to ground on the wiper of each of the input potentiometers.  While not conducive to prototyping you may want to even replace these with fixed value resistors to remove such unknowns.

    c)      Try replacing all of the potentiometers with equivalent fixed value resistors and try to re-create the failure.

    Without much knowledge of the application or why the INA326 was selected, you may be interested in exploring other single-supply INAs such as the INA333.  We also have programmable gain amplifiers that may be of interest.

    I hope this helps.