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Phase-Shift Oscillator ...

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randolfo

New Member
I have this circuit, phase-shift oscillator (see attached). I don't know which of the following choices are the frequency-determining components?



1) R2 and R5
2) R1 and R2
3) C1 and R3
4) R1 and C4

I am confused on the two choices 3 and 4 , I am not sure which one to go to? Could you please give me an insights on these two? I am inclined to choose no. 4, hopefully you will help me clear my confusion.. Thank you.
 

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audioguru

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R2 is in parallel with R5.
 

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randolfo

New Member
Thanks for the reply . I became confused with the circuit , is it phase-shift oscillator or wien bridge oscillator?
 

audioguru

Well-Known Member
Most Helpful Member
You can also look in Google to see a Wien Bridge oscillator that is different.
 

BrownOut

Banned
If you read the link I provided in my first post, you can read all about phase shift and wien bridge oscillators.
 

audioguru

Well-Known Member
Most Helpful Member
R2 is the input impedance of the inverting opamp circuit. It is effectively in parallel with R5 so affects the frequency and amount of phase shift.

Maybe you should add a buffer opamp (that has a high input impedance) so that R5 is not loaded down and the new opamp drives R2.
 

audioguru

Well-Known Member
Most Helpful Member
Good idea.
But the oscillator has highpass phase-shift networks that boost distortion. The distortion will be pretty high anyway since there is nothing to keep the opamp from clipping.
 
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