Talk:Circuit Idea/Slowing Circuit Processes

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) 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 of 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 of 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 of a cause and of the output voltage as of 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)