Talk:Circuit Idea/How to Understand Circuits

I start the discussion by moving a part of discussion about negative resistance phenomenon from the Wikipedia Archive_4 talk page about negative resistance. Circuit-fantasist (talk) 18:36, 4 March 2009 (UTC)Circuit-fantasist (talk) 20:19, 20 February 2009 (UTC)

Thinking of an op-amp as an integrator
...Really, how op-amps work is a key point to understanding op-amp circuits. When I was a student in middle 1970s, reading classical explanations (they still exist) I couldn't understand what and how an op-amp really does in op-amp circuits with negative feedback. Later, in middle 1980s, when I began explaining basic op-amp circuits with negative feedback to my students, I realized gradually a paradoxical fact: although an op-amp is really a proportional and, as they consider, an almost "non-inertial" device, in order to understand how op-amp circuits work, we have to think of it as an integrating, inertial device what it actually is (see also op-amp myths, Integrator inside section). Figuratively speaking, we have to think of the op-amp as a "being" that "observes" continuously its input voltage and changes its output voltage until it manages to zero the input voltage. If we think of the op-amp in terms of UOUT = A.VIN (i.e., VIN and UOUT change simultaneously), we fall into a vicious circle traveling the feedback loop and we can never understand circuit operation. We have to assume that the output voltage stays late regarding the input voltage. More philosophically speaking, we have to see the causality in the op-amp operation; to think of the input voltage as a cause and of the output voltage as a result. Quite later I found this concept in The art of electronics, "The golden rules" section (p. 177): What the op-amp does is "look" at its input terminals and swing its output terminal around so that the external feedback network brings the input differential to zero (if possible). As you can see, Horowitz & Hill have also animated the inanimate op-amp with the sole purpose of showing what it actually does in negative feedback circuits. Circuit-fantasist (talk) 20:19, 20 February 2009 (UTC)

How to present circuits to people
(a copy from the Wikipedia Archive_4 talk page about negative resistance. Circuit-fantasist (talk) 18:52, 4 March 2009 (UTC)

Believe me (I have been explaining circuits to young people for decades), the best way of presenting circuits to people is to show the circuit evolution. The final result is not so important for understanding circuit ideas; the movement from the imperfect initial circuit solution to the final perfect one is the most important. If we want people really understand circuit solutions, we have first to show why the initial (usually passive or transistor) circuit is so "bad" and then to make it perfect by means of electronics according to some clever idea. Circuit-fantasist (talk) 14:01, 22 February 2009 (UTC)

What does "to understand circuits" mean?
(a copy from the Wikipedia Archive_4 talk page about negative resistance. Circuit-fantasist (talk) 18:56, 4 March 2009 (UTC)

It is more than obvious that, in order to create this part of the article, we (Wikipedia editors, responsible for it) have to understand all these op-amp circuits. Otherwise, it would be very confusing if we "explain" these circuits to people but the very we do not know what the basic ideas behind them are. But what does "to understand circuits" mean?

Generally speaking, it means to find out all about each of the components constituting the circuit: why it is added to the circuit, what its function is, what it does, how it does it, what its value has to be, etc. Then we have to discern groups of components constituting familiar sub-circuits and to clarify its role. Especially for the present op-amp circuits we have to know the role of the positive impedance element connected between the op-amp output and the non-inverting input,  the role of the voltage divider connected between op-amp output and the inverting input and, of course, the role of the very op-amp. Please, answer the concrete questions below and suggest possible circuit explanations. Circuit-fantasist (talk) 15:37, 22 February 2009 (UTC)