Can you honestly formulate such a condition that will encompass ALL the possible marginal combinations required in order to fully answer the question the OP has asked.?
A simple yes or no, would suffice.
E.
That's a good question, and I've never seen a good conclusive answer on this.
By the way (because I`ve got the impression that you don`t like continuing this thread):
hi,There are already more than 500 contributions in the following thread - and it seems they didn`t come yet to an agreement if there is a current or not.
So you think there is no reasonable conclusion? Some things that are more complicated take more time to resolve. Perhaps you think this is not the forum for such a discussion?
I guess I'm just not following your logic here. It seems that suddenly you dropped the gain>1 and gain compression criteria. While my mind can see how #6 might tie in to both of those conditions, and could possibly replace them (too subtly for my taste), I don't see why #3, which relates to startup energy, should replace those. I don't know about Winterstone, but that is too theoretical for me, even if I get to the point of understanding it. I don't see why sufficient conditions should not be very clear and obvious, and more in line with things we need to do to actually make the oscillator.I mentioned #3 because if we have the oscillation frequency then we shouldnt need loop gain > 1. Barkhausen didnt need that right? But maybe this is more theoretical then Winterstone wants to be right now.
Are you talking about "planets and a sun" or "solar cells and a battery"?One of the other things i wanted to stress is that if the power supply turn on is too slow, the oscillator may not start. This could happen in a system like a solar system. Should we worry about this? It's interesting and it does happen so i think we should.
The question i asked you before was how did you see one oscillator work and the other didnt work. The standard worked and the inverted oscillator did not work when you did a simulation i guess. Then i mentioned the two gain resistors. Then you said you had them right.
Well what i was driving at was if you set the resistors correctly (slightly off from their ideal values) you should be able to see both oscillators either:
1. Have an amplitude that rises continuously until the output saturates.
2. Have an amplitude that falls continuously until it reaches zero output.
3. Have an amplitude that stays constant for a very long time.
Winterstone said:"For R6=9.75k oscillation starts, but with decreasing amplitudes - indicating stability. For 10.2k oscillation also start - but with rising amplitudes until limiting (supply rail) with latch-up effect.
(However - this applies for the idealized opamp model only. Real models cause a real pole in the RHP causing instability for all values of R6. This is logical because the real opamp cannot find a stable bias point - we have 100% positive dc feedback)."
I think Winterstone didn't quite get this understanding when he commented in post #102. He mentioned "only one complex pair allowed..." and "no real pole". But, even without the real pole, we see a latchup at the rails because the gain saturates and the pole pair moves from LHP to RHP, which causes the latch. We need the pole pair to move from the RHP to the LHP when gain<1. So, I think my statement is worded in a very simple and useful way. Full stability is a good sufficient condition (in conjunction with other conditions too, of course) to require for the linearized model when G<1.
This is why I think that the gain-compression and the stability for gain<1 are important for this discussion, and are good candidates to consider as the core for sufficient conditions for oscillators made in the way we typically make them.
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