Notch Oscillator

No buggzy, what you offer here is, you do not understand the principle of harmonic oscillators. The way you have choosen the configuration of the double t notch filter and the way how you tried to compensated this with a positive feedback shows you haven't understand the basics of harmonic oscillators.

Hey, as long as it oscillates, it works. That’s all that really matters, right? Just getting a working example is the first step. Understanding can probably come later.

@jason9, build it test it and see what it does for you irl! Good luck.

As I’m sure you remember why, I can’t do that. As to why it doesn’t work, at first I thought that perhaps the terminals of the op-amp were flipped from how they should be, but after experimentation in the sim I’ve found out that that is not true. Could you please explain why it won’t work, @hurz?

I have never said it doesn't do any oscillation in real. But the way it might do is bullshit and against anything you might have learned about such kind of oscillators. A perfect notch filter does drop infinite the amplitude, so buggzy struggles with the gain. An oscillator amplifier needs some input and if its a 180° phase shift one (inverting amplifier) it does the additional 180° so we come to 360°! But as buggzy does not know that basic he struggle with zero input at phase shift point he need and as very dirty “solution“ he took that additional positive feedback to overcome the almost infinite attenuation of its notch, which is in simulation endless and inreal even more endless because the notch will not be as perfect symetric and thats the point were i can see he does not made this circuit in real. So again, phase shift oscillator needs and external network to make 180° and an inverting amplifer which equalysis the attenuation of the phase shifter. Take out the filter and experiment were it does 180° phase shift and how much attenuation you get. Do that as little homework (im not your teacher) but if you want to learn, just do it. Maybe buggzy can follow without knowing already everything. Task, this oscillator can only work in real because of tollerances of filter components, which we dont have in buggzys circuit here!!!

Check this simple circuit “Perfect Notch Oscillator does not exist“ http://everycircuit.com/circuit/6181026199240704 hope you can see it

Maybe this way over its hash code 6181026199240704

Jason, are you still there? Cuz we are not finished in understanding! Can you follow what i have said so far?

Sorry, I’m still here. Just for some reason forgot to come back to this thread.

Ok. I understand. I’ll post a circuit of a proper notch oscillator now.

Posted.

Excellent, we are closer and closer to what this “notch filter oscillators“ really is 👍! But now a little step back ... i continue on your posted circuit. Why is this oscillator working, and why on this frequency? To answer this we must go to bode plot, everycircuit nicest feauture since its born 😁