Phase-Shift Oscillator ... - Electronic Circuits Projects Diagrams Free

randolfo · 19th October 2009, 05:28 PM

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.

BrownOut · 19th October 2009, 05:32 PM

C1, c2, c3, r3, r4, r5

Read This

audioguru · 19th October 2009, 05:47 PM

R2 is in parallel with R5.

randolfo · 19th October 2009, 06:56 PM

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

bloki · 19th October 2009, 07:13 PM

Phase-shift oscillator - Wikipedia, the free encyclopedia

audioguru · 19th October 2009, 09:58 PM

You can also look in Google to see a Wien Bridge oscillator that is different.

BrownOut · 20th October 2009, 12:07 AM

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

randolfo · 20th October 2009, 07:37 AM

Quote:

Originally Posted by BrownOut

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

Thanks. I will do that...

randolfo · 20th October 2009, 07:05 PM

Quote:

Originally Posted by audioguru

R2 is in parallel with R5.

Sorry audioguru, What does it mean R2 is in parallel with R5 ? R2 and R5 is the correct choice?

audioguru · 20th October 2009, 07:45 PM

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.

The Electrician · 21st October 2009, 04:23 PM

How about eliminating R5 and making R2 the same value as R3 and R4, then adjusting R1 for the proper gain? Since the - input of the opamp is a virtual ground, R2 will then properly load the last section of the phase shift network.

See: Phase-shift oscillator - Wikipedia, the free encyclopedia

Of course, no provision has been made for amplitude stabilization.

audioguru · 21st October 2009, 08:44 PM

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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19th October 2009, 05:28 PM	#1
randolfo	Phase-Shift Oscillator ... 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. Attached Thumbnails

19th October 2009, 05:32 PM	#2
BrownOut	C1, c2, c3, r3, r4, r5 Read This __________________ You don't need a quadraphonic Blaupunkt -- you need a curve ball. Last edited by BrownOut; 19th October 2009 at 05:37 PM.

19th October 2009, 05:47 PM	#3
audioguru	R2 is in parallel with R5. Attached Thumbnails __________________ Uncle $crooge

19th October 2009, 06:56 PM	#4
randolfo	Thanks for the reply . I became confused with the circuit , is it phase-shift oscillator or wien bridge oscillator?

19th October 2009, 07:13 PM	#5
bloki	Phase-shift oscillator - Wikipedia, the free encyclopedia

19th October 2009, 09:58 PM	#6
audioguru	You can also look in Google to see a Wien Bridge oscillator that is different. __________________ Uncle $crooge

20th October 2009, 12:07 AM	#7
BrownOut	If you read the link I provided in my first post, you can read all about phase shift and wien bridge oscillators. __________________ You don't need a quadraphonic Blaupunkt -- you need a curve ball.

20th October 2009, 07:45 PM	#10
audioguru	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. __________________ Uncle $crooge

21st October 2009, 04:23 PM	#11
The Electrician	How about eliminating R5 and making R2 the same value as R3 and R4, then adjusting R1 for the proper gain? Since the - input of the opamp is a virtual ground, R2 will then properly load the last section of the phase shift network. See: Phase-shift oscillator - Wikipedia, the free encyclopedia Of course, no provision has been made for amplitude stabilization.

21st October 2009, 08:44 PM	#12
audioguru	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. __________________ Uncle $crooge