Need help deriving the transfer function of a phase shift oscillator

JoeJester

Joined Apr 26, 2005
4,390
Very true....very true. I only went to that linked document to get examples of other circuits.

Hopefully the TS will come back.
 

MrAl

Joined Jun 17, 2014
8,616
LVW, I do realize it's three section filter that attenuates the signal which has to be amplified for oscillation. The example on the tutorial stated the output was 6.5 kHz. Ok, I don't know what you expect, but when someone states it's 6.5 kHz I expect it to be within 5000 parts per million of 6.5 kHz. You might not, and that is fine. Yes, I do know there are poles in the op amp that can and do affect the output frequency.

Mr Al, I agree the simulators can be finicky. I did break out the sections from the circuit to view the outputs of each section when the source was 6.5 kHz to observe the phase shift and attenuation. I also know about the need for some initial conditions, charge on capacitors when working with some oscillating circuits. Getting it to a sine was was always the objective and getting it within some semblance close to 6.5 kHz is always nice as well.
I could try to reproduce your results if you tell me exactly what you did.
Then i could see for myself what you were talking about.
 
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