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Questions related from Cyril Mechkov
When saying "resistance", we imagine something (a kind of resistor) connected between two points. Then what do we imagine when talking about "differential input resistance" of a BJT differential...
24 March 2019 6,951 33 View
I dedicate this question to my students from Faculty of Computer Systems and Technologies of TU Sofia (groups 44, 45, 46 and 47)... A few months ago, I asked a similar question (surprisingly,...
23 March 2018 4,535 7 View
I have been thinking for a long time on the so-called "Early voltage". What interests me is whether there can be some physical explanation of this quite artificial definition. IMO this concept...
17 February 2018 7,741 15 View
In the conventional start/stop relay circuit, an additional ("holding") contact is connected in parallel to the start push button. But what do we do when there is no such an additional contact?...
05 December 2017 1,624 10 View
In the laboratory of Digiital circuits, we conduct two separate exercises dedicated to latches and Schmitt triggers. But I am deeply convinced that there is no principal difference between these...
26 November 2017 1,427 10 View
To build the most elementary storage cell (latch, SRAM cell) we take a non-inverting amplifier (Fig. 1) and simply connect its output to the input (Fig. 2). For some reasons, we implement this...
21 November 2017 980 15 View
I use a lot of effort to reveal the role of the common emitter current source (the "long tail") in the differential pair to my students. I do this by first justifying the need for a (whatever)...
11 November 2017 1,867 13 View
In the early 80's, I invented a series of LED indicators based on the same powerful idea - a diode element connected in parallel to another diode element with a higher threshold voltage, diverted...
11 November 2017 201 11 View
In the diploma thesis of my graduate Erol Kerim, I noticed an interesting circuit of a modified current mirror (in the attached picture). It made me think again about this strange circuit solution...
03 August 2017 5,004 33 View
We can make an attenuator act as an amplifier by connecting it in the negative feedback of an...
26 November 2016 4,401 24 View
Once presented, in a form of a balanced...
10 October 2016 6,880 16 View
Once presented the abstract circuit of a negative impedance converter (NIC) as a bridge...
05 October 2016 688 41 View
We have seen a balanced bridge circuit in the basic circuit of...
30 September 2016 791 33 View
I dedicate this question to Abdelhalim Zekry as an appreciation for his competent comments posted in the right place at the right...
24 September 2016 986 18 View
Once clarified what "load line" exactly means... https://www.researchgate.net/post/What_is_actually_a_load_line_and_can_this_concept_be_presented_in_a_more_attractive_way_to_students ...now it...
08 May 2016 7,683 6 View
As already I shared with you, my students and I managed to unravel many of the mysteries of the mere potentiometer in the first lab on Basic circuitry dedicated to resistive passive...
15 March 2016 5,898 89 View
As a rule, the BJT common-emitter output characteristics are presented as a function of the collector current IC of two variables - the collector-emitter voltage VCE and the base current IB; IC =...
22 September 2015 9,623 21 View
The output characteristic of the common-base stage is a horizontal line (the first attached picture)... and of the common-emitter stage - a slightly inclined line (the second picture). But what is...
10 September 2015 1,784 23 View
I have asked this question with two purposes - first, at the request of Barrie Gilbert to terminate the irrelevant discussions in the question...
28 December 2014 2,891 45 View
To build electronic circuits, first of all we need the natural electrical elements resistors, capacitors and inductors. However, in many cases we are not satisfied with the performance of these...
16 September 2014 7,444 19 View
Negative feedback systems compensate disturbances in the feedback loop by adding extra power equal to the power dissipated in disturbing elements. So they can be considered as negative impedance...
03 August 2014 7,916 77 View
In op-amp inverting circuits, we can think of the op-amp output voltage as of extra voltage equal to the voltage drop across the positive element connected between the output and the inverting...
31 July 2014 618 3 View
The negative impedance concept is so attractive that some authors try to bring it on even the most basic electrical elements as voltage and current sources. See as an example the work of this...
14 June 2014 3,134 81 View
When discussing whether there is a connection between the transistor common-base stage and the op-amp inverting...
01 June 2014 7,837 100 View
In all the op-amp inverting circuits (transimpedance amplifier, inverting integrator and differentiator, diode log and antilog converters, etc.), the op-amp compensates the voltage drop across the...
01 June 2014 2,443 100 View
Are they based on a common basic idea? If so, what is it? Can we see it in other circuits? Is this only a specific electronic idea? If it is more general, can we see it in our life? It is always...
20 May 2014 3,974 22 View
Microcomputers are dynamic devices that are synchronized by a clock oscillator. So the signals (E, R/W, CS, A15-A0, D7-D0) appear on their buses only for parts of a microsecond and, as the buses...
22 March 2014 8,203 19 View
It is well known that Google puts Wikipedia pages on the first places in its results list, and for many people it seems that they are the best sources sought by them. But is this really so? From...
23 November 2013 7,844 26 View
Can we believe it? Can we rely on them? And to what extent? Looking at Wikipedia from the outside (as a reader), it seems perfect with its highest Google rank. But here I want to look at it from...
05 November 2013 5,256 66 View
I temporarily leave the “kingdom” of my favorite analog electronics and move to the neighboring field of digital electronics because this term I will conduct a series of labs in the laboratory on...
08 October 2013 2,810 17 View
We have already discussed reactive elements in the questions below but I have asked here this separate question to consider thoroughly the way they oppose input voltage sources when connected in...
04 October 2013 9,169 35 View
When we need some voltage that is different from (less than) the power supply, the humble voltage divider from Ohm's times is the simplest solution. Thus the combination of the supply voltage...
21 September 2013 4,366 3 View
It is a common practice to consider the voltage divider as a voltage source, e.g. to say, "the circuit is supplied with a constant voltage by a voltage divider". Also widespread is the resistor to...
20 September 2013 632 41 View
I restore my participation in RG discussions by asking the next "naive question" about basic electrical phenomena from the Ohm's times. I can not figure out why I do it since, in fact,...
18 September 2013 5,367 69 View
When we see somewhere written "negative resistance", we are never sure what exactly it is, just because it has two varieties - "true" and "differential"... and the former is not a resistance:) We...
01 September 2013 3,029 29 View
Once virtually destroyed the ohmic resistance of a...
13 August 2013 4,602 3 View
We can enlarge the powerful idea of the “ideal” op-amp ammeter already discussed in the question below by replacing the movement with other current-driven loads (2-terminal elements like LEDs,...
12 August 2013 2,621 16 View
By adding a “helping” voltage to the voltage drop across a resistor (real ammeter with internal resistance), we have virtually zeroed its resistance thus building the perfect op-amp...
12 August 2013 8,412 10 View
I remember that many years ago when I was a student and I had to construct an electronic measuring instrument with a simple movement indicator of how much I was deeply impressed by this extremely...
05 August 2013 3,918 34 View
I cannot imagine a simpler negative feedback system than an inverting voltage amplifier whose output is connected to its input. In the most sophisticated case, this circuit can be implemented by...
06 June 2013 5,182 11 View
I continue asking "provocative" questions about the nature of the ubiquitous negative feedback phenomenon and its wordly manifestations. In the question below, I have expressed my speculation that...
06 June 2013 8,666 15 View
I can't imagine more "elegant simplicity" than these two twisted wires. It is invented in the distant 1881 by Bell in telephony (what's an invention - to twist two wires!), but imagine we can see...
14 May 2013 3,803 59 View
The extremely interesting and topical questions below were about the rift between digital and analog...
10 May 2013 7,786 21 View
Op-amp amplifiers with negative feedback are implemented in two versions - non-inverting and inverting. I have asked this question with the purpose to initiate a discussion about the main...
04 May 2013 9,068 39 View
This question is dual to the question below that I asked a few hours...
20 April 2013 3,006 7 View
This is another question from the series of "provocative" questions about the odd, exotic and paradoxical circuit solutions that should not exist but they still exist-:) I ask them with the...
20 April 2013 8,242 7 View
I continue asking more and more unusual, odd and, sometimes, a little "provocative" questions-:) about the most fundamental circuit ideas with the purpose to demolish the dominating formal, dull...
18 April 2013 3,495 15 View
Is it well known that the transistor is an active element used to build amplifiers. But IMHO this is not true. The transistor is not active but passive element; the only thing that a transistor...
01 April 2013 5,045 97 View
It is well known that the voltage divider (two resistors connected in series) is a unidirectional device where we apply the input voltage across the whole network and take the partial voltage...
28 March 2013 1,071 15 View
This discussion is old as the very bipolar transistor... but it is still interesting... In my opinion, a BJT can be controlled either by voltage or current depending on the situation. If we want...
24 March 2013 1,869 100 View
After all the epic discussions-:) about the Wien bridge oscillator... https://www.researchgate.net/post/What_is_the_basic_idea_of_Wien_bridge_oscillator_How_does_it_operate ...I have finally...
09 March 2013 6,552 16 View
I have extracted these questions from the discussions (leaded by Lutz von Wangenheim) about the Barkhausen criterion, RC oscillators and phase shift in RC circuits where we tried to answer the...
28 February 2013 9,367 99 View
It is well-known that there is a 90 deg phase shift between the current and voltage in the capacitor (when supplied by a sinusoidal signal) and it varies from 0 to 90 degrees in the RC integrating...
13 February 2013 8,416 54 View
I dedicate this discussion to the XXVIII International Scientific Conference Electronics - ET2019 ( https://e-university.tu-sofia.bg/e-conf/?konf=24 ) where, in 1997, I first presented my...
01 January 1970 8,365 42 View
01 January 1970 6,428 17 View
I dedicate this story to my students from groups 48 and 49, ITI Traditionally, at the beginning of the first lab on Semiconductor Devices, I remind my students of Electrical Engineering basics....
01 January 1970 2,445 29 View
It is well known that there is a linear relationship between the BJT collector and base current (Ic = beta x Ib). It would be interesting to explain it in an intuitive way. The power of such a...
01 January 1970 2,290 4 View
The ingenious circuit solution of Howland current source (aka "pump") was invented by Prof. Bradford Howland of MIT, about 1962 (see Fig. 5 on page 7 in the material...
01 January 1970 9,616 7 View
