Activity for Circuit fantasist
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Comment | Post #286900 |
@Tony, thanks for the interesting observations. I am glad to see that you are not only a great circuit designer but also a "circuit philosopher". I will try to add some of my views to your philosophy...
▪︎ In my opinion, "eliminate the Vbe diode voltage offset from the input" is because the trans... (more) |
— | over 1 year ago |
| Comment | Post #285107 |
@Tony, I think when there is a resistor connected between the emitter and the supply rail, that's another story named *negative feedback* ("emitter degeneration")... (more) |
— | over 1 year ago |
| Comment | Post #286900 |
@Tony, What is the common terminal in the circuit of a common-emitter stage with emitter degeneration? It should be a point with fixed voltage... but there is no such point. All the transistor terminal voltages are varying... (more) |
— | over 1 year ago |
| Comment | Post #286900 |
@Tony, the very title of this story specifies that it is about the idea - the structure, the topology of the circuit solution. Inventing the circuit and calculating it are different things - the former is something qualitative; the second is quantitative. It is incorrect to explain qualitative things... (more) |
— | over 1 year ago |
| Comment | Post #286215 |
@TonyStewart, you got me thinking again about the difference between "voltage" and "voltage drop"... and I think I found an even better answer than before...
I think that when we charge a capacitor from a voltage source, there is a voltage across the source and a voltage drop across the capacitor;... (more) |
— | over 1 year ago |
| Comment | Post #286215 |
It is interesting to answer such a question, "What is across a capacitor - voltage or voltage drop?" (more) |
— | about 2 years ago |
| Comment | Post #285392 |
I understand... Thanks for the comment though. (more) |
— | about 2 years ago |
| Comment | Post #285392 |
I guess you have some reason to write this... but I can't guess what.
According to my ideas, the internal resistance of the input sources is added to the resistance of the input resistors. As a result, the gain of the inverting and non-inverting input of this simple differential amplifier becomes ... (more) |
— | about 2 years ago |
| Comment | Post #285392 |
Thank you for the useful feedback. I have planned to make a similar story about basic transistor circuits. Happy New Year! (more) |
— | over 2 years ago |
| Comment | Post #285392 |
Thanks! Happy New Year! (more) |
— | over 2 years ago |
| Comment | Post #285392 |
Thanks for the fair opinion. I will redraw the two voltage diagrams illustrating only the input part with the three resistors. It is also possible to split the article into two parts - in the first, to remain only building the circuit in six steps (the structure evolution), and in the second, to cons... (more) |
— | over 2 years ago |
| Comment | Post #284995 |
I agree with your arguments. I used the resistance because it is the most primary quantity that leads to a change in the other quantities (current and voltage).
I think in such a way: The diode is a passive element that does not produce or accumulate energy. So, the only thing it can do, is to ch... (more) |
— | over 2 years ago |
| Comment | Post #283942 |
Yes, this is a small exception... So, if we connect two photodiodes in a loop, they will compete and this network will act like a "dynamic load"? If so, this will be a very sensitive differential photo sensor... (more) |
— | over 2 years ago |
| Comment | Post #283942 |
"The essence of the ideal current source is quite simple" because it is presented in a formal way in textbooks. As a result, students only superficially know what a current source is - just as a definition and as a circle with an arrow inside that keeps the current constant. But they do not know how ... (more) |
— | over 2 years ago |
| Comment | Post #283942 |
Here is another point of view on this issue. The dynamic resistor (transistor) plays only the role of a self-regulating element that determines the current produced by the voltage source just as the transistor in an amplifier plays the role of a regulating element. In both cases, for the purposes of ... (more) |
— | over 2 years ago |
| Comment | Post #282696 |
This view may work well in a formal circuit analysis but not for the purposes of the intuitive circuit understanding where the source is source... and the resistor is a resistor... (more) |
— | over 2 years ago |
| Comment | Post #283942 |
In electronics, we use a more clever trick to make almost "ideal" (perfect) current sources - we keep the voltage constant but vary the resistance when some disturbance (e.g., the load) tries to change the current. So, the resistance is not infinite but "dynamic".
In the transistor implementation... (more) |
— | over 2 years ago |
| Comment | Post #283942 |
Okay, I did not want to delve into the essence of the ideal current source, but I will clarify.
The ideal current source is an element but, for the purposes of intuitive understanding, we need to know what is inside it… since there are no genuine current sources in nature… and we have somehow to m... (more) |
— | over 2 years ago |
| Comment | Post #282696 |
I was happy to read your answer because it really gives a good intuitive explanation... but I have a few remarks.
Regarding the function of Q2 and Q4, what are they? "Passive current sources" and "controlled variable resistance" do not sound well since they are neither sources nor (ohmic) resistan... (more) |
— | over 2 years ago |
| Comment | Post #283587 |
It is possible that OP question has another meaning, namely, "After turning on the power, in what state are the outputs of the circuit? Which is HIGH and which is LOW?" (more) |
— | over 2 years ago |
| Comment | Post #278555 |
@Elliot Alderson, Are you happy with my answer? If this circuit solution seems too complicated to you, I will offer you an even simpler recipe for "converting" SPST into SPDT switch - only through a "pulling" resistor. It was dominant before the complementary stage was invented... (more) |
— | over 3 years ago |
| Comment | Post #279860 |
When I clicked the "insert picture" button, nothing happened and I did not see the window "insert an image". But I just tried it and it already works... (more) |
— | over 3 years ago |
| Comment | Post #279860 |
OK, I found it by search. JavaScript is enabled. (more) |
— | over 3 years ago |
| Comment | Post #279860 |
I have seen Javascript void (0) in the lower left corner of the screen. BTW I use Chrome but I have the same problem when using IE and Opera as well. I can not find where to enable JavaScript (Settings -> Advanced -> Content settings? ...) (more) |
— | over 3 years ago |
| Comment | Post #278933 |
... So far, the transistor is able to resist the input voltage through its emitter voltage. Now the latter disappears and the input voltage is applied directly through the base-emitter junction to the emitter (load). In some cases, this is undesirable... and in others it can be useful. BTW we can obs... (more) |
— | over 3 years ago |
| Comment | Post #278933 |
@coquelicot, Thanks for the comprehensive explanation. I imagined something similar but now it is quite clear to me. As you probably noticed, in my circuit stories I try to show non-standard circuit ideas. My goal is to arouse interest in creative thinking leading to invention of circuits. In this st... (more) |
— | over 3 years ago |
| Comment | Post #278933 |
@coquelicot, can you explain to me what does "tinkerer solution" ("tinkerer") mean? I guess but I am not sure... (more) |
— | over 3 years ago |
| Comment | Post #279596 |
@LvW, Exactly... I just quoted an excerpt from another similar question that was asked to me some time ago... (more) |
— | over 3 years ago |
| Comment | Post #279580 |
@Michaël Bensimhoun, Let's stop here. We exchanged interesting thoughts that give us food for thought. I am happy with that. Thanks for the comments. (more) |
— | over 3 years ago |
| Comment | Post #279580 |
The problem of such a "BJT constant-current diode" is that it needs another (base) input voltage in addition to the voltage drop across the emitter resistor. The emitter voltage is subtracted from the base voltage and the positive difference (in the case of an NPN transistor) is applied as a bias vol... (more) |
— | over 3 years ago |
| Comment | Post #279580 |
Regarding the RD circuit supplied by the collector voltage, I mean that when the load resistance varies, the transistor (no matter how "muscular" it is) will change its collector-emitter voltage VCE to compensate the load resistance variations... and this voltage supplies the Zener diode through a re... (more) |
— | over 3 years ago |
| Comment | Post #279580 |
Regarding the decoupling capacitor, I mean that it is always a bad idea to quickly charge a capacitor... But really, in this case it has a small capacitance and this is not such a problem. (more) |
— | over 3 years ago |
| Comment | Post #279580 |
Regarding the first (genuine) circuit diagram: The voltage drop across the resistor depends on the base and load current... and accordingly, on the magnitude of the ripples. So, I suppose, there is some kind of a self regulation of the voltage across the capacitor to the ripples. (more) |
— | over 3 years ago |
| Comment | Post #279580 |
Regarding "the simplest possible activated current source, and hence, also, current limiter": It can be considered as a dual BJT version of the JFET "current diode" with a resistor in the source. However, here there is a need for an external reference voltage obtained by a Zener diode and a resistor... (more) |
— | over 3 years ago |
| Comment | Post #279580 |
Regarding the trick with the Zener diode in parallel to the resistor: If the capacitor has not so small capacitance, it can be decoupled in the first moment by a diode connected between the capacitor and base (with the cathode to base); the Zener diode should be connected after the diode, to the base... (more) |
— | over 3 years ago |
| Comment | Post #279580 |
I am trying to recall my comment accidentally deleted during the update: "Perfectly written paper with a lot of philosophy and various implementations. I guess it will also be of interest to you [What does this transistor circuit do?](https://electronics.stackexchange.com/questions/532326/what-does-t... (more) |
— | over 3 years ago |
| Comment | Post #279527 |
Perfectly written article with a lot of philosophy and specific implementations... I would add also an interesting link to [What does this transistor circuit do?](https://electronics.stackexchange.com/questions/532326/what-does-this-transistor-circuit-do/)
(more) |
— | over 3 years ago |
| Comment | Post #279431 |
I should make a "little" correction to one of my comments above. Connecting a voltmeter in parallel to the diode will not introduce an error because the voltage across it is produced by a voltage source. Rather this will be a problem in the case when the diode is driven by a current source (the dual ... (more) |
— | over 3 years ago |
| Comment | Post #279431 |
@coquelicot, nice circuit diagram... Do you realize this is the well-known non-inverting configuration where TD is R1 and AM2 is R2? Or, this is the well-known "non-inverting current source" where TD is a "functional voltage-to-current converter" and AM2 is a "current-to-movement converter" (analog ... (more) |
— | over 3 years ago |
| Comment | Post #279431 |
... Of course, the ammeter will be floating. So in this solution either the voltmeter or ammeter are floating... but still there is a solution in which both are grounded. (more) |
— | over 3 years ago |
| Comment | Post #279431 |
Another suggestion - put the ammeter into the feedback loop (between the op-amp output and the common node where the inverting input and diode are connected). There are two benefits of this trick: first, the op-amp will raise its output voltage to compensate the ammeter resistance; second, both the d... (more) |
— | over 3 years ago |
| Comment | Post #279431 |
A good answer to my comment above… and demonstration of creative thinking… but there is another problem. If "the voltage is measured at the terminals of the diode with the multimeter", and the voltmeter is not perfect, it will divert a part of the current through the diode… and an error will appear. ... (more) |
— | over 3 years ago |
| Comment | Post #279431 |
Simple and clear explanation... Now only the milliammeter resistance can create a problem. If only we can hide it somehow... (more) |
— | over 3 years ago |
| Comment | Post #279413 |
Attractive experiment... If the load line could be shown... (more) |
— | over 3 years ago |
| Comment | Post #279016 |
Ooooo ... now I just saw the simulation. Really very attractive and beautiful ... Thanks for the effort ... maybe it will help me to see something new in the solution. I like your idea to show two simultaneously acting versions - with and without bias. This shows the effect of bias. Do you agree wit... (more) |
— | over 3 years ago |
| Comment | Post #279016 |
@TonyStewart, Yes... but these wonders of today are only means that cannot replace the need for thinking. Because it is very unfortunate and comical to master them perfectly but not to understand what the ideas behind circuits are... and this is a ubiquitous phenomenon today. And it leads to this ... (more) |
— | over 3 years ago |
| Comment | Post #279016 |
Regarding your second comment, my goal is to show how the inventor thinks when a new idea conceives in his/her mind. This initial stage of the circuit development is the most obscure and least considered. For this purpose, I use a specific circuit in which there is some trick and therefore it was rec... (more) |
— | over 3 years ago |
| Comment | Post #279016 |
@TonyStewart, Thanks for the advice. Indeed, handmade drawings are not the usual technique today. I use them because they give me more freedom in exposing my ideas. In the 90s, I was using Corel Draw and in the 00s, Macromedia Flash animator. Then I started drawing schematics on a white board and wh... (more) |
— | over 3 years ago |
| Comment | Post #279030 |
@LvW, I am trying to explain your simulation results through my graphics... but there is something that bothers me. According to my graphs, such good linearity could only be obtained if the resistor would be dynamic ("current sink") because its curve then would be horizontal. How can you explain this... (more) |
— | over 3 years ago |
| Comment | Post #279050 |
@ coquelicot, Thomas Hayes is a unique person with a circuit philosophy and subtle sense of humor. I was deeply impressed by his Student manual. I even dedicated a funny Flash movie (https://www.circuit-fantasia.com//collections/tools/strange-things.html) to him and then created an interactive "circ... (more) |
— | over 3 years ago |