INA128: about INA128 output impedance

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

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