Timeline for How to determine the input resistance of a bootstrapped emitter follower
Current License: CC BY-SA 3.0
12 events
| when toggle format | what | by | license | comment | |
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| Dec 28, 2017 at 0:30 | comment | added | S.s. | Yes and no, the beta stated in the data sheet is 40, I was using a beta of 70 which is the one stated in the SPICE model of the transistor, and apparently the author used 100 for no particular reason, but this is all speculation because no mathematical derivations are included in the book. | |
| Dec 27, 2017 at 21:25 | comment | added | Neil_UK | my bad, you did what I asked, but that wasn't what I meant. I meant without C2, with r3/r4 driven by a different but perfect bootstrap source, say another copy of the input voltage source, with 2 or 3 10ks on the emitter. This was to see what the tranny beta effect alone was. However, I see from the other answer, you were using the wrong value for beta. Duh! | |
| Dec 27, 2017 at 21:16 | history | edited | SamGibson♦ | CC BY-SA 3.0 |
Fixed spelling (e.g. emmiter -> emitter), capitalisation of multiplier (e.g. K -> k), added units of Ω, split some sentances to reduce "wall of text", all to try to improve readability.
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| Dec 27, 2017 at 20:56 | vote | accept | S.s. | ||
| Dec 27, 2017 at 19:55 | answer | added | G36 | timeline score: 1 | |
| Dec 27, 2017 at 18:22 | history | edited | S.s. | CC BY-SA 3.0 |
deleted 3 characters in body
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| Dec 27, 2017 at 18:10 | comment | added | S.s. | Without C2, the simulator gives a 89k, vs the 84 kohm theoretical value, and without C2 but with an additional 10K resistor the simulator gives 82K VS 75k theoretical value. | |
| Dec 27, 2017 at 8:36 | comment | added | Neil_UK | I'm with you on your reasoning, bootstrapping removes the loading effect of R3, but places an addtional 10k load on the emiiter. What does your simulator give as input impedance without C2? What about without C2, but an additional 10k (so three total) loads to ground from the emitter? | |
| Dec 27, 2017 at 6:05 | history | edited | S.s. | CC BY-SA 3.0 |
[Edit removed during grace period]; edited body
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| Dec 27, 2017 at 5:52 | history | edited | S.s. | CC BY-SA 3.0 |
edited body
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| Dec 27, 2017 at 5:43 | history | edited | S.s. | CC BY-SA 3.0 |
added 17 characters in body
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| Dec 27, 2017 at 5:36 | history | asked | S.s. | CC BY-SA 3.0 |