Activity for LvW
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Comment | Post #287728 |
No input signal? Therefore, does the circuit produce this output? Oscillation? (more) |
— | over 1 year ago |
| Comment | Post #287435 |
Using the keyword "Slew Rate" you will find a lot of information in the internet. (more) |
— | over 1 year ago |
| Comment | Post #287689 |
I agree to everything Olin L. has stated.
Moreover, all commonly used formulas are (and must be) "inaccurate".
Typical example: The often used closed-loop gain expressions for opamps (-R2/R1 or (1+R2/R1)) are only approximations because many secondary effects are neglected (input/output impedances... (more) |
— | over 1 year ago |
| Comment | Post #287689 |
@Olin Lathrop: Of course, I know that a phrase like "as clean as possible" says nothing. On the other hand, a "hobbyist of electronics" has certainly not a good feeling for "what is possible". Therefore, one should explain to him (and that`s what I have always done in similar situations) why the osci... (more) |
— | over 1 year ago |
| Comment | Post #287689 |
I think, when a "hobbyist of electronics" uses a wording like "pure stable sinewave" he is referring to a sinusoidal output "as clean as possible" - in contrast to other oscillators (which, I think, should better be called "generators") producing squarewaves or other signal forms.
At least, this w... (more) |
— | over 1 year ago |
| Comment | Post #287678 |
Quote: "Until now all the topologies that I have found if the frequency is changed, a change in the circuit component is mandatory here is some topologies: :
Courtesy of TEXAS INSTRUMENTS".
How do you want to tune the frequency if not by "changing" one or more circuit element(s)? More than that, ... (more) |
— | over 1 year ago |
| Comment | Post #287435 |
Please note that the "10% to 90%" criterion is valid for small-signal responses only. The slew rate is a large signal parameter (valid for opamps with heavy feedback) which requires that the first stage is saturated for a very short time until feedback brings it back to linear operation. (more) |
— | over 1 year ago |
| Comment | Post #287366 |
I am not sure if this comment is an appropriate answer to an unexperienced forum member...("deliberately disrespectful"..).
(more) |
— | over 1 year ago |
| Comment | Post #287211 |
Sorry, but I have problems to agree.
To me the quantity F is the feeedback factor - which is identical to "the fraction of the output fed back to the negative input" (your definition) .
That means: F is always smaller than unity.
Example: Feedback resistor is R2 and resistor R1 is from the inv. ... (more) |
— | over 1 year ago |
| Comment | Post #287211 |
You wrote: Gain = F / (1 + F/G).
When G is the open-loop gain and F the feedback factor , the closed-loop gain is (according to Blacks famous formula):
Gain Acl=G/(1+F*G) (more) |
— | over 1 year ago |
| Comment | Post #286689 |
You wrote: "A single pole low pass filter isn't totally flat up to the rolloff frequency...".
From this, one could derive that there is a multi-pole filter which is "totally flat" up to the roll-off frequency - but this is not possible, (more) |
— | over 1 year ago |
| Comment | Post #286793 |
Just to avoid misunderstandings - the feedback network does not contain any lowpass filters.
The oscillators working principle is as follows:
The feedback network of a Hartley oscillator consists of a 3rd-order HIGHPASS filter in classical lader topology: Ro-L1-C1-L2.
This highpass introduces... (more) |
— | almost 2 years ago |
| Comment | Post #286784 |
@Concerned Citizen: I must admit that I cannot agree to your conclusion that "their value is chosen such that it doesn't influence the overall oscillator".
While it is true that the finite input resistance of the transistor stage has only a minor influence on the pole frequency of the R-L-C-L hig... (more) |
— | almost 2 years ago |
| Comment | Post #286784 |
It seems that the given expression for the pole frequency contains a small error :
For L1=L2 the pole frequency is w²=1/2LC.
With your formula it is 1/4LC.
However, the given condition for oscillation is correct (based on the mentioned assumptions and simplifications).
Nevertheless - one additio... (more) |
— | almost 2 years ago |
| Comment | Post #286738 |
There is a contradiction in the title of your contribution.
A small-signal analysis is possible (makes sense) only in case of a linear (in practice: quasi-linear) region of the transfer function.
Saturation mode is a heavy non-linear mode and is defined for the case that BOTH pn-junctions are forwa... (more) |
— | almost 2 years ago |
| Comment | Post #286700 |
@ MissMulan You were asking "why is that true" that the transfer function is defined for sinusoidal signals only. I think, definitions cannot be "true" or "false" - definitions are arbitrary determinations which are logical and make sense.
The transfer function T(s) of a system is derived from its f... (more) |
— | almost 2 years ago |
| Comment | Post #286700 |
Quote: "The transfer function is a description of what happens with any input signal."
What is the meaning of "any input signal"?
To avoid misunderstandings it should be clear that the transfer function is defined for sinusoidal signals only! (more) |
— | almost 2 years ago |
| Comment | Post #286679 |
Let me try to "translate" your requirements:
Lowpass (no order specified) with -3dB at fo=100 Hz
A frequency increase beyond this frequency fo by another 100Hz (fx1=200 Hz) must correspond to a damping of -10dB (because of 0.1dB/Hz).
A first-order lowpass (fo=100 Hz) has a damping of -10 dB ... (more) |
— | almost 2 years ago |
| Comment | Post #286589 |
So I ask myself: What is the purpose of a comments section? Not to clarify misunderstandings/misconceptions? (more) |
— | almost 2 years ago |
| Comment | Post #286589 |
Why not? I am really surprised. For my understanding it directly concerns the question (from Miss Mular). He/she was asking for the role of re=1/gm where gm is a quantity which connects the input VOLTAGE with the output CURRENT. And the transconductance gm is the key parameter for the explanation of... (more) |
— | almost 2 years ago |
| Comment | Post #286589 |
continued: To understand your position it would be great if you would mention to me one single application (circuit) where the current-controlled view has advantages during design of the circuit and/or for a better understanding. (more) |
— | almost 2 years ago |
| Comment | Post #286589 |
Quote: "...most of the electrons that leave the emitter get swept away to the collector before they have a chance to come out the base. That view is definitely current-dominated."
My response: I cannot share such a view. What means "dominated" in this context? When most of the electrons leaving th... (more) |
— | almost 2 years ago |
| Comment | Post #284538 |
When discussing feedback we always have two basic parts: (1) An active device and (2) a feedback path. Without such a feedback path (which closes the feedback loop) there is no feedback at all - we have a so-called "open-loop gain". In the case under discussion, the resistor Re constitutes the feedba... (more) |
— | over 2 years ago |
| Comment | Post #284538 |
Quote (last sentence): "You can think of an emitter follower as working on internal feedback in the transistor."
Negative feedback ist realized by the emitter resistor - not "internal...in the transistor". (more) |
— | over 2 years ago |
| Comment | Post #283942 |
Quote Elliot Andersen: "The essence of the ideal current source is quite simple, and trying to convert it to a voltage source and some kind of magic dynamic resistor only makes it harder to understand."
I strongly disagree. Who can UNDERSTAND (from the technical/physical point of view) an element ... (more) |
— | over 2 years ago |
| Comment | Post #282363 |
Quote: "You can keep asking "why" questions indefinitely. "Why is grass green?" "Then why is chlorophil green?" "What makes it look green to us?" ..."
Sorry for my silly question. However, when you make a statement without sufficient evidence I think it is legal to ask for explanation - to the benfi... (more) |
— | almost 3 years ago |
| Comment | Post #282363 |
Quote:"When VIN- is a little below VIN+, that is more current than Q2 can sink, so VOUT goes high". Of course, I agree - however, what is the clear explanation? WHY goes Vout high? We have two (non-ideal) current sources with a conflicting behaviour. How and why does this fact influence the voltage a... (more) |
— | almost 3 years ago |
| Comment | Post #282434 |
You ave nothing to do than to solve for iout and set ic2=-ic1 and ic3=ic4 - that`s all. (more) |
— | almost 3 years ago |
| Comment | Post #281322 |
I must admit - a rather strange discussion...... (more) |
— | about 3 years ago |
| Comment | Post #279596 |
Quote:..."in the differential resistance, the difference is between two voltage values at adjacent values of the current." Did the questioner (Pacifist) spoke about resistances? I think, he has mentioned instead a differentiating circuit. In this case, we could speak about two adjacent voltages at t... (more) |
— | over 3 years ago |
| Comment | Post #279588 |
OK - I was of the opinion that in a short comment it would be appropriate to use the well-known abbreviations for the open-loop gain Aol and the closed-loop gain Acl. The quantity beta was defined using the symbols shown in the drawing. Again, I like to point out that for sinusoidal signals it is, of... (more) |
— | over 3 years ago |
| 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) |
— | over 3 years ago |
| 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) |
— | over 3 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) |
— | over 3 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) |
— | over 3 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) |
— | over 3 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) |
— | over 3 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) |
— | over 3 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) |
— | over 3 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) |
— | over 3 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) |
— | over 3 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) |
— | over 3 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) |
— | over 3 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) |
— | over 3 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) |
— | over 3 years ago |
| Comment | Post #278630 |
I am polite and do not comment on this fascinating math lesson. (more) |
— | over 3 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) |
— | over 3 years ago |
| Comment | Post #278637 |
Thank you for your answer. But: What means "voltage-stable" and "current-stable" in this respect? (more) |
— | over 3 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) |
— | over 3 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) |
— | over 3 years ago |