Timeline for Why are these voltage regulators seemingly using positive feedback?
Current License: CC BY-SA 4.0
9 events
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| Nov 7, 2023 at 21:41 | history | edited | Designalog | CC BY-SA 4.0 |
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| Nov 3, 2023 at 10:49 | history | edited | Designalog | CC BY-SA 4.0 |
added 18 characters in body
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| Nov 3, 2023 at 8:04 | comment | added | Virgil_Tibbs | Thank you, I think I am starting to vaguely understand it. Would it be acceptable to send you an email with my attempt of analyzing the circuit? And you could, If you deem appropriate and not too big of a bother, provide me with some feedback to my inevitable errors? | |
| Nov 3, 2023 at 7:54 | comment | added | Designalog | If you have more questions, check out my profile to reach me. | |
| Nov 3, 2023 at 7:51 | comment | added | Designalog | @Virgil_Tibbs Think of it as simple non-inverting voltage amplifier. There, you also have both input terminals swinging in the same direction such that the error signal equals 0. To know that the feedback is negative, you can simply do the mental exercise that there's a voltage disturbance in any node (voltages goes either up or down, you can choose arbitrarily). Then, once you follow the loop, the conclusion must be that loop suppresses this voltage swing (at least it works for this kind of feedback topology). | |
| Nov 3, 2023 at 7:37 | comment | added | Virgil_Tibbs | This is confusing. I know that in order for the feedback to be negative the loop gain should be negative. Is this applicable here, as well? Where do you break the loop, at the drain of pass transistor? And you input a test voltage at the upper end of R1? | |
| Nov 3, 2023 at 7:20 | comment | added | Designalog | You have to follow the inversions in the signal chain. In this case, voltage amplification means series feedback at the input: there has to be a subtraction between 2 input voltages. If vref swings up, for negative feedback to function properly, voltage at (+) terminal must be also be swinging up. If you find a contradiction to that, there's no negative feedback. | |
| Nov 3, 2023 at 7:18 | comment | added | Virgil_Tibbs | Well I got to admit that I was working from the assumption that negative feedback meant a direct connection between the output and the inverting input. | |
| Nov 3, 2023 at 7:05 | history | answered | Designalog | CC BY-SA 4.0 |