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| 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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