Original question:
OPA277: About Open-loop output impedance of the PSpice model
Part Number: OPA277
How would you test for this op amp's open loop output impedance vs frequency and dc physically? Are the inductor and capacitor there only for simulation or are small values needed in real life? And how would you apply a current (with and without a frequency) to the output? I tried it with a resistor and voltage waveform generator but it doesn't seem to be accurate.
The large value inductor and capacitor used in the output impedance over frequency simulation are there to isolate the output Zo from being effected by finite input impedance.
In practice, you would apply at the output a small-signal IG1 sine current source (e.g. 100uA) at different frequency, 10mHz, 1kHz, etc. and back calculate, Ro=Vo/IG1, at any given frequency - see below.
For Zo measurement at 1kHz you could use 1H and 1mF as shown below BUT for lower values of LT and C1 the measurement will be corrupted my Zin.
