buddypoor wrote on Dec 7th, 2011, 12:19am:But the example I have presented is quite different, I think. Using the idealized opamp model the results don't only deviate up to a certain degree from the correct behaviour, but there is a fundamental difference beween real and ideal: works vs. works not at all.
Thus, there is no chance for the designer to "weigth and take into account the limitations of the model he's running".
I will tell you something about the background of my posting:
There is one author -very well known in the analog world - who has published a paper in an international electronic magazine (also with very good reputation) dealing with an "oscillator circuit" (how he calls it) that never will work in practice. It is a modification of the classical WIEN oscillator - however, all analyses are based on an ideal opamp model only. In detail, he is discussing oscillation condition, frequency, amplitude stabilization - for a "circuit" that never will oscillate in case of real opamps (immediate saturation due to net positive dc feedback).
And my original question was if such a combination of active and passive parts may be called "oscillator".
What do you think?
Regards
Hi Buddypoor,
I still think it is a matter of being aware that you are dealing with a model - and not a real circuit - during the design phase. The ultimate question is: how well the model represents the circuit you are trying to build? And I think that question applies to the example of the published "oscillator circuit" you pointed out, that only works with ideal components.
It is up to the designer to evaluate the limitations (considering second order effects introduced by actual circuits) of the model which was used for developing the circuit. In the publication you cited, if that was not done, then the analysis was incomplete and the validity of it is under question, as reality proved it.
In my opinion, your example is an example of an "oscillator circuit model" and not and "oscillator circuit": if you are talking about circuits you are talking about real stuff...not models.
Best
Tosei
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