Timeline for What is an op-amp's differential input impedance?
Current License: CC BY-SA 4.0
7 events
| when toggle format | what | by | license | comment | |
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| Apr 6, 2021 at 19:40 | vote | accept | Jonah F | ||
| Apr 6, 2021 at 19:40 | |||||
| Apr 6, 2021 at 19:34 | comment | added | Jonah F | Thanks for the follow up, makes sense now. | |
| Apr 6, 2021 at 19:33 | comment | added | Andy aka | And R4 becomes part of the common mode impedance equation rather than anything related to differential input impedance. | |
| Apr 6, 2021 at 19:29 | history | edited | Andy aka | CC BY-SA 4.0 |
added 24 characters in body
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| Apr 6, 2021 at 19:27 | comment | added | Andy aka | You can regard both inputs as being connected to Vx via their respective resistors R1 and R3. Nothing else matters. Don’t forget, that a proper diff amp has both those resistors as the same value to cancel common mode noise. | |
| Apr 6, 2021 at 19:08 | comment | added | Jonah F | Ok, thank you. Am I right in saying that R4 is not in the final result because R4 directly controls the value of Vx, and since both V+ and V- have the same voltage (Vx) the 'effect' of R4 is present in both inputs, and so when we take the difference it gets lost? | |
| Apr 6, 2021 at 19:03 | history | answered | Andy aka | CC BY-SA 4.0 |