Timeline for Where did Bootstrapping get its name?
Current License: CC BY-SA 3.0
19 events
| when toggle format | what | by | license | comment | |
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| Nov 6, 2016 at 17:52 | comment | added | LvW | Please, see my comment to Olin Lathrop`s answer. | |
| Nov 6, 2016 at 17:48 | comment | added | LvW | ...emitter degeneration is POSITIVE feedback??? | |
| Nov 6, 2016 at 17:46 | comment | added | D.A.S. | same yes. so negative feedback and positive feedback often consider just voltage and emitter degeneration is positive feedback <1 and same for bootstrap | |
| Nov 6, 2016 at 17:45 | comment | added | LvW | I must admit that I don`t understand the term "inverted voltage feedback". Do you mean "negative" voltage feedback? | |
| Nov 6, 2016 at 17:43 | comment | added | D.A.S. | of course impedance feedback ratio is most important as long as feedforward gain or open loop is sufficient which may be expressed voltage or current as well | |
| Nov 6, 2016 at 17:40 | comment | added | LvW | Possible cause of misunderstandings: Saying "VOLTAGE feedback" I always mean "current or voltage controlled VOLTAGE feedback". The same for CURRENT feedback: It can be "voltage or current controlled CURRENT feeedback". That means: I am always referring to the quantity that is fed back and NOT to the quantity that controls the feedback signal. | |
| Nov 6, 2016 at 17:40 | comment | added | D.A.S. | perhaps miscommunication from brevity causes misunderstanding, but common emmiter with Rf is inverted voltage feedback or current sensed on Rc routed via Rf to Rb impedance | |
| Nov 6, 2016 at 17:31 | comment | added | LvW | No - negative feedback of a voltage ALWAYS increases Zin (example: Effect of emitter resistor). Negative feedback of a current (example RB between collector and base) always reduces Zin. | |
| Nov 6, 2016 at 16:46 | comment | added | D.A.S. | so negative voltage feedback lowers Zin and Zout at those end points while positive feedback does the opposite and if Vgain>=1 in latter, it oscillates or becomes hysteresis | |
| Nov 6, 2016 at 16:44 | history | edited | D.A.S. | CC BY-SA 3.0 |
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| Nov 6, 2016 at 16:37 | history | edited | D.A.S. | CC BY-SA 3.0 |
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| Nov 6, 2016 at 15:57 | comment | added | LvW | I don`t understand the sentence "negative current feedback is positive voltage feedback". We have negative voltage feedback (due to RE) and positive current feedback (due to the bootstrap path). And both effects cause input impedance increase. | |
| Nov 6, 2016 at 15:27 | comment | added | D.A.S. | yes but as you see, negative current feedback is positive voltage feedback with gain <1... hence positive bootstrap | |
| Nov 6, 2016 at 15:26 | comment | added | LvW | I think, to avoid misunderstandings, we should state instead: Negative voltage feedback always increases and negative current feedback always decreases the input impedance of an amplifier. | |
| Nov 6, 2016 at 15:20 | comment | added | D.A.S. | this only applies to the points where neg feedback is applied, not alternate inputs. e.g for common base, with 2nd stage inverting feedback to 1st stage emitter input, its emitter output z must be reduced with base cap to allow negative feedback into emitter or non-inv OA uses alternate input. | |
| Nov 6, 2016 at 9:02 | comment | added | LvW | TonySteward, how can you say that "negative feedback lowers input&output impedance"? What about Re-feedback for transistor stages and non-inverting opamps with neg. feedback? | |
| Nov 5, 2016 at 18:45 | history | edited | D.A.S. | CC BY-SA 3.0 |
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| Nov 5, 2016 at 17:15 | history | edited | D.A.S. | CC BY-SA 3.0 |
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| Nov 5, 2016 at 17:06 | history | answered | D.A.S. | CC BY-SA 3.0 |