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INA128: output impedance

Carl Wolfe
Genius 10645 points
Part Number: INA128

what is the output impedance of the INA128? 

is there a way to calculate/estimate from information provided in the data sheet?

  • 0
    TI__Guru* 93105 points

    Hi Carl,

    The INA128 uses an all NPN output so the open-loop Zo will likely be complex and change with frequency, which of course will be reflected in the closed-loop Zout. 

    I don't see anything in the datasheet that would allow us to estimate the closed-loop Zout. I am checking to see if we measured the INA128 Zout at any time. 

    Regards, Thomas

    Precision Analog Applications Engineering

  • 0 in reply to Thomas Kuehl
    TI__Guru* 93105 points

    Hi Carl,

    The INA128 Zout information was sent to you directly via email.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to Thomas Kuehl
    Prodigy 30 points

    Hello Thomas,

    I am also interested in obtaining the INA 128 Zo information as I am interfacing it with a data acquisition unit and need a good understanding of its impedance. If you could send that to me as well I would really appreciate it.

    Thank you,

    Mike

  • 0 in reply to Michael Cino
    TI__Guru* 93105 points

    Hello Mike,

    See the INA128 closed-loop Zout graphs that I have pasted below. The two curves in each graph are labled Iq/8 and Iq/2. What that indicates is the dc current the output is sourcing, or sinking, relative to the device's operating current, Iq. Since the INA128 typical Iq is 700 uA, so Iq/8 is 87.5 uA and Iq/2 is about 350 uA.

    Regards, Thomas

    Precision Amplifiers Applications Engineering