Timeline for Question about differential signals and feedback
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jun 15, 2021 at 8:30 | comment | added | user288518 | In the last picture (with corrections made...), you can not say that the red signals are "differential" because one point is grounded. You can speack only of an "error input" which can permit the OPamp to be functional. You can split eventually this "error" in differential and common mode signals while redesigning theoritical schematic. But no need to do so. Input - is a virtual ground. So Ad can be used. | |
| Jul 27, 2019 at 8:29 | comment | added | Stefanino | I made a mistake because I copied the schematic of my book, but this is not the problem: obviously the source of M9 must be connected to a negative voltage. The doubt I have still remains: how can be proved (if I'm right) that the red signals are differential? | |
| Jul 26, 2019 at 21:14 | comment | added | KalleMP | +2 I was going to comment on this but see that you point it out neatly. From the first reading and the OPs first diagram I was nervous about below rail input operation and erroneous assumptions leading from there as a start. | |
| Jul 26, 2019 at 13:46 | comment | added | devnull | I see your point. Thanks for clarifying. The lack of symmetry would break the "ac ground" assumption that facilitates the differential gain analysis. | |
| Jul 26, 2019 at 13:26 | comment | added | Stefanino | Yes, you're right, that node must be connected to VSS and not ground. However, even if I adjust the schematic as you correctly said, my doubt still exists: in order to use Ad, we should have those red differential signals (because Ad was found under that hypothesis); how to prove (if I am right) that they are differential? Thank you | |
| Jul 26, 2019 at 13:15 | history | answered | devnull | CC BY-SA 4.0 |