Activity for LvW
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Comment | Post #279030 |
......but it is linearized due to negative feedback effects if the transistors are used as followers See my update (EDIT) in my detailed answer. (more) |
— | about 4 years ago |
| Edit | Post #279030 |
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| Edit | Post #279030 |
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| Edit | Post #279030 |
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| Edit | Post #279030 |
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| Comment | Post #279022 |
Yes - very strange. It can lead to the (false) assumption that the output current Id would be an amplified version of the (parasitic) input current. (more) |
— | about 4 years ago |
| Edit | Post #279030 |
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| Edit | Post #279030 |
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| Edit | Post #279030 |
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| Edit | Post #279030 |
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| Edit | Post #279030 | Initial revision | — | about 4 years ago |
| Answer | — |
A: Using FET based followers and design rules "Also, if there is a way to control this drop (without using an oamp), what are the design rules, or perhaps the rules of thumbs ?" "I reformulate this question:do you see any reason to use a FET follower?" (1) As outlined by Olin Lathrop, the voltage drop (that means: The potential differenc... (more) |
— | about 4 years ago |
| Comment | Post #278636 |
I'm sorry that I had to say this here so clearly, but I think that false information in a serious forum should not remain unchallenged. (more) |
— | about 4 years ago |
| Comment | Post #278636 |
(Quote): "However, for the purpose of circuit design, the current-controlled model of a BJT is a lot more useful in my experience." My answer: There is not a single circuit which can be explained exclusively with current-control only. But in contrarty: There are many circuits which work (and can be e... (more) |
— | about 4 years ago |
| Comment | Post #278760 |
(Quote):"...mixing two different concepts ...: Whether people recognize the names you used above to know the circuits, and whether they know of real life uses for those circuits." I did not ask if somebody is able to recognize the names. I think, if somebody can answer my question about commercial ap... (more) |
— | about 4 years ago |
| Comment | Post #278760 |
I must admit that I am disappointed. Did I express myself not clear enough? Many active blocks have been introduced in the past - I have mentioned some of them. And the only thing I am interested in is to learn if any member of this forum knows about a commercial realization/application of one of the... (more) |
— | about 4 years ago |
| Comment | Post #278760 |
@Olin Lathrop. Could be that I was not able to express myself clear enough (English is not my mother tongue!). I am only interested to learn if one (or more) of these novel active building blocks has more than a theoretical meaning only. That is all! For example: The AD844 is an integrated circuit th... (more) |
— | about 4 years ago |
| Edit | Post #278760 |
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— | about 4 years ago |
| Comment | Post #278760 |
I am aware that most of the names are not very well known - and that's why I ask. I am sure that someone will only answer if he has a positive example for a professional application. Of course, I cannot and do not want to present any circuit diagrams or even explanations here. It is something like a... (more) |
— | about 4 years ago |
| Edit | Post #278760 |
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— | about 4 years ago |
| Edit | Post #278760 | Initial revision | — | about 4 years ago |
| Question | — |
Usage of modern active building blocks In the past, a large number of new active building blocks have been proposed and published by many researchers all over the world. In most cases, these new building blocks were used for realizing novel filter and/or oscillator circuits. In addition to the well known amplifier types Operational... (more) |
— | about 4 years ago |
| Edit | Post #278616 |
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— | about 4 years ago |
| Edit | Post #278616 |
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— | about 4 years ago |
| Comment | Post #278614 |
Yes - it is really a challenging task to select the proper filter topology for a specific application. Under IDEAL conditions (no tolerances, ideal active units) all alternatives are equal. The differences become visible only under real conditions (parts tolerances, real amplifiers). And there are e... (more) |
— | about 4 years ago |
| Comment | Post #278614 |
@coquelicot. Just to answer your question: GIC means "Generalized Impedance Converter" - here shown in a form introduced by Antoniou (other forms are possible, but this is the best concerning sensitivity to opamp non.idealities.). Several years (decades) ago it was shown that this GIC-block is the mo... (more) |
— | about 4 years ago |
| Comment | Post #278637 |
@Circuit fantasist. Thanks for the link to the RG discussion. As I can see, I even took part in the discussion - my memory!!
But: This discussion is an excellent example of how experts can answer a question briefly but factually and meaningfully... (more) |
— | about 4 years ago |
| Comment | Post #278617 |
Thank you for this comment. Yes - it is and was my primary goal to UNDERSTAND circuits as well as design procedures. And to clarify contradictions, which undoubtly do still exist! And, therefore, I consider it still as absolutely necessary to discriminate between practical rules for designing circuit... (more) |
— | about 4 years ago |
| Comment | Post #278617 |
A pity - it is of course rather easy to speak of "incorrect statements"..... without naming a single one....good luck. (more) |
— | about 4 years ago |
| Comment | Post #278630 |
@coquelicot. I have seen your edit in your answer...I did the same: My response is written as an EDIT in my answer. (more) |
— | about 4 years ago |
| Edit | Post #278617 |
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— | about 4 years ago |
| Comment | Post #278630 |
I am polite and do not comment on this fascinating math lesson. (more) |
— | about 4 years ago |
| Comment | Post #278636 |
@Olin L. Sorry, but one last comment (question): Since there are some points in your answer which I cannot agree upon (more or less: fundamental insights), I like to ask you if I may contact you by email? Could be an interesting exchange of facts and opinions ... (more) |
— | about 4 years ago |
| Comment | Post #278637 |
Thank you for your answer. But: What means "voltage-stable" and "current-stable" in this respect? (more) |
— | about 4 years ago |
| Comment | Post #278630 |
OK - stop here if you like. No problem for me. However, I am a bit surprised: You have repeated all the well-known equations Ic=exp(Vbe/Vt)....and your final conclusion is Ic=f(Ib). I cannot follow this logic - perhaps I am too old... (more) |
— | about 4 years ago |
| Comment | Post #278630 |
Perhaps I misunderstood your 99.9%? It was a bit unclear. My position: App. 60% of relevant published sources speak about voltage -control Ie=f(Vbe). See Ebers-Moll and Gummel-Poon. Do you need examples or proofs? Your last line shows a correlation, which is OK. However, it must not misinterpretet. ... (more) |
— | about 4 years ago |
| Comment | Post #278636 |
Here is a simple example which can explain my view regarding theory and practice: For finding the voltage across one of the resistors as part of a voltage divider we assume that the current I produces a voltage corresponding to V=I*R. This works always fine. But it is not in accordance with theory. T... (more) |
— | about 4 years ago |
| Comment | Post #278636 |
@Olin Lathrop. Sorry, but another comment is unavoidable: (Quote) "You can argue the physics both ways, since its not black and white." Both ways? I rather think that each observable physical effect has exactly one cause which clearly can be identified. Exception: Basic natural laws like gravity etc... (more) |
— | about 4 years ago |
| Comment | Post #278630 |
continue... As you have mentioned the Ebers-Moll model description: Exponential relation Ie=f(Vbe). Am I wrong? (more) |
— | about 4 years ago |
| Comment | Post #278636 |
@Circuit fantasist. "Compromise formulation": "...set the voltage across the base-emitter junction by passing an appropriate current through it". So - voltage results from current? What then is the role of the voltage divider at the base (less-resistive as possible/allowed)?
(more) |
— | about 4 years ago |
| Comment | Post #278636 |
My fault: I have tried to make a clear distinction between (a) practical aspects and (b) physical effects. It seems I did not sucseed. Many good books and many publications from leading US-universities have convinced me that the BJT is voltage-controlled. But that was not my question here (just an in... (more) |
— | about 4 years ago |
| Comment | Post #278630 |
@coquelicot. No - I cannot agree at all. However, I don`t intend to discuss again the question current vs. voltage control (show me one single proof that Ib would determine/control Ic). Regarding the emitter follower: It can be best explained starting from the feedback effect caused by RE: current-co... (more) |
— | about 4 years ago |
| Edit | Post #278617 |
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— | about 4 years ago |
| Edit | Post #278617 | Initial revision | — | about 4 years ago |
| Answer | — |
A: Why Ib=const. for BJT output characteristics Ic=f(Vce) My Answer: There are only practical reasons for a representation with Ib=const. These characteristics are primarily used to determine the DC working point (Ico, Vceo) - together with the working line (resistors Rc and Re). Would it be helpful and useful to be able to read the corresponding ... (more) |
— | about 4 years ago |
| Edit | Post #278616 | Initial revision | — | about 4 years ago |
| Question | — |
Why Ib=const. for BJT output characteristics Ic=f(Vce) Introduction: In some books and other technical papers (also from universities) it is - surprisingly - still claimed that the bipolar transistor (BJT) would be a current-controlled element. This is simply stated - without any explanation or proof (which I think is impossible). But of course, the... (more) |
— | about 4 years ago |
| Comment | Post #278613 |
Not "ideal" - but "idealized" and as "good" as possible with such a simple arrangement. (more) |
— | about 4 years ago |
| Edit | Post #278613 | Initial revision | — | about 4 years ago |
| Answer | — |
A: Purpose of emitter resistor in a common collector amplifier In most cases, the common-collector stage (emitter follower) is used as a buffer stage (unity gain). It is, therefore, an independent stage, whose mode of operation should not be determined by the next stage (which is to be decoupled). That means: Even without a connected load this stage should o... (more) |
— | about 4 years ago |
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