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INA128: about INA128 output impedance

Joyce Li
Intellectual 2170 points
Part Number: INA128
Other Parts Discussed in Thread: TINA-TI

Hi Dear Expert,

What is the output impedance of INA128, datasheet didn't list this spec, can you please help answer?

BR,

Joyce. 

  • 0
    Guru 140200 points

    Hi Joyce,

    the output impedance is very low, but depends on gain and load. In an usual application with a gain of 100 and a signal frequency of 1kHz the output impedance is under 1Ohm. You can run a TINA-TI simulation with the INA128 TINA-TI reference design and see for yourself.

    Keep in mind, though, that the output current is limited. See figures 13, 14 and 15 of datasheet.

    Kai

  • 0
    TI__Guru 64840 points

    Joyce,

    There is a fundamental difference between the open-loop (Ro) and close-loop (Rout) output impedance and their understanding is critical in solving stability issues.  Ro is controlled by the internal circuit topology while Rout is a function of the specific circuit configuration used: Rout = Ro / (1+Aolβ)


     

    Please review the attached presentation - Op Amp Stability vs Output Impedance.

    Op Amp Stability vs output impedance.ppt

  • 0 in reply to Marek Lis
    TI__Intellectual 2170 points

    hi Marek,

    thanks very much for your support!

    Joyce