Showing posts from February, 2021

Is there a circuit element which dissipates energy but does not act as a resistor?

My answer  to SE EE question  Is there a circuit element which dissipates energy but does not act as a resistor? [closed] Many interesting psychological phenomena can be observed in StackExchange. One of them is the closing of interesting, non-standard and original questions by people having more limited thinking.  Such people have the ability to quickly unite into something resembling Russian  " NKVD troika ".  As a result of this filtering, the platform is full of monotonous and boring questions.  Here is another example... My answer OP: ... is there an energy sink which does not alter the properties of the circuit? Yes, there is such a "sink"; its name is "transimpedance amplifier" - Fig. 1a. In this conceptual circuit diagram, the op-amp output is represented by the variable voltage sourve VOA. Fig. 1. Transimpedance amplifier - a conceptual circuit diagram (circled in blue). It consists of two elements in series - a resistor R2 and a variable voltage

Моята творческа автобиография (без илюстрации)

  Творческа автобиография на Кирил Мечков Идвайки в света на техниката 1954- 1959.   На 08.04.1954 съм се появил на този свят...  Някъде на около 5 години, направих първото си „изобретение“ – хидравличен интегратор (воден часовник). За целта пробих една пълна с вода консервена кутия, и с интерес наблюдавах как изтича водна струя, а нивото на водата бавно спада. Това беше първата ми среща с флуидните величини от вида поток и налягане, които по-късно ми помогнаха да си обясня и да обяснявам електрическите величини ток и напрежение. Първи срещи с електричеството 1964. На около 10 години, бях очарован от магията на електричеството. Първото електрическо устройство, което истински ме заинтригува, беше един постояннотоков звънец, подарен ми от познат електротехник. За мен беше истинска мистерия как камбанката вибрираше сама, но успях да си го обясня... Това ми помогна да направя и първото си електрическо „изобретение“ - нещо подобно на инерционните сензори в алармените системи. Аз прикр

Are there "inverted relays"?

My answer  to SE EE question  Are there "inverted relays"? This story is another very recent example of how the questions asked in SE EE awaken my creative activity. Thanks to the experience I have from electronic circuits, I was able to explain in a new (for me) way how the operation of the humble electromechanical relay can be reversed. My answer Short answer: A relay can be "inverted" by "inverting" either the coil (connecting to Vcc) or contacts (make them NC). Structure. A relay consists of two cascaded parts (stages) - an input part (coil) and an output part (contacts). They can be considered as a kind of "converters" with input and output: the coil converts the input voltage into a magnetic field and armature movement; the contacts convert the armature movement into a resistance (on/off circuit). Each of them can be "noninverting" and "inverting" so that a total of four combinations are possible. To make an "inve

Trying to understand how this pnp works

My answer  to SE EE question  Trying to understand how this pnp works I have been familiar with this BJT driving technique for a long time... but now I came up with a new original explanation through a "dynamic resistor" concept... Answer OP:  How can this pnp be turned off? A more in-depth conceptual answer to this question can be given if the main BJT input property is taken into account:  BJT can be more easily controlled by voltage than current since its input base-emitter junction behaves as a voltage-stabilizing element . This property can be seen in its input IV curve having an almost vertical part. This means we can control it more easily by small voltage changes instead of large current changes. So, the problem of turning off the transistor only by an "opto" is that we try to do it by decreasing the current instead of the voltage… and it opposes us. Let's see how... The output collector-emitter part of the photo-transistor can be thought of as a varying

Universal (magic) Op-Amp Fundamentals

My answer  to SE EE question  Universal (magic) Op-Amp Fundamentals This question touched me with its sincerity and caused (for some time) my indignation at the soulless teaching. It took me far back in my student years when I was trying to figure out what the idea behind basic computing analog devices was... My answer Essence. This professor's creature can be called "universal summing-subtracting op-amp circuit" (not "universal op-amp" since the op-amp is just one of the circuit components). It reminds me of the distant past when analog computers tried to compete with digital ones... but soon lost that battle (analog computers consisted of building blocks and this was one main block). Structure. The curcuit consists of two passive resistor summing circuits and an op-amp: The upper 4-input summer consists of the four resistors R1, R2, R3 and Rf. The first three are connected to the external input voltage sources V1, V2 and V3; the "feedback" resistor