Electronics > Beginners

Measuring Output Impedance of a 741

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eev_carl:
Thanks everyone.  I'll do the Colorado lab tonight!

Audioguru:

--- Quote from: eev_carl on August 09, 2018, 03:57:29 pm ---Is this link mentioning that the output resistance is 75 ohms for the 741 is relevant?  I'm keeping my frequency constant.
--- End quote ---
Since the open loop gain of the old 741 opamp is about 8000 at 100Hz and the gain is set to 10, then the output impedance is about 1 ohm.
The output impedance is about 75 ohms at DC with no negative feedback and at a high frequency where there is little open loop gain, because then there is no negative feedback to reduce it.

My calculation for the output impedance at 100Hz might be wrong. I have never calculated or measured the output impedance of an opamp, but I know that negative feedback reduces the output impedance of an amplifier. 

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