Multiloop and inverting configuration

martioz · 5th March 2003, 12:47 AM

Is this a correct implementation of the multi-loop feedback into inverting Op amplifier buffered circuit?
Hence inverting input has lower distortion I’m trying to configure feedback loop and overall gain.

Any comment is more than welcome.

martioz · 5th March 2003, 12:49 AM

Damn, forgot attach,
Edit:
Cannot see attachment

martioz · 5th March 2003, 12:51 AM

trying again...
Edit:
can't post attachment

maybe link works:
http://www4.head-fi.org/forums/attac...&postid=312006

phase_accurate · 5th March 2003, 07:36 AM

Your outer loop generates positive feedback !!

Regards

Charles

Circlotron · 5th March 2003, 08:56 AM

Yeah, two cascaded inverting amps make a non-inverting amp! Add a third stage. Other than that, you want to return R4 to the junction of R2 and R3.

martioz · 5th March 2003, 11:24 PM

Thanks for pointing this out; I was half asleep when I post it.

I hope now the circuit is correct, the idea is to use two inverting opamps to get non-inverted signal.
Get inner loops to stabilize opamps and outer loop to adjust required gain.

Link:
http://www4.head-fi.org/forums/attac...&postid=312845

But I think, since this circuit is to be used as a "gain clone", let’s say gain about 100, the function of the outer loop losing functionality.

martioz · 6th March 2003, 12:15 AM

Corrected Attachment (Link):

http://www4.head-fi.org/forums/attac...&postid=312898

Circlotron · 6th March 2003, 12:48 AM

*Every* connection to U1 pin 2 needs a resistor in series. The top opamp output hasn't got one in series with it's output to U1 pin 2 like it should.

martioz · 6th March 2003, 01:31 AM

Is it better to return signal from the output of the feedback opamp to the point in front of R2 instead of adding extra resistor to the global loop?

Tube_Dude · 6th March 2003, 02:17 AM

No...its not!

It need the resistor!

5th March 2003, 12:47 AM	#1
martioz diyAudio Member Join Date: May 2002 Location: Melbourne	Multiloop and inverting configuration Is this a correct implementation of the multi-loop feedback into inverting Op amplifier buffered circuit? Hence inverting input has lower distortion I’m trying to configure feedback loop and overall gain. Any comment is more than welcome.

5th March 2003, 12:49 AM	#2
martioz diyAudio Member Join Date: May 2002 Location: Melbourne	Schematic Damn, forgot attach, Edit: Cannot see attachment

6th March 2003, 02:17 AM	#10
Tube_Dude diyAudio Member Join Date: Mar 2002 Location: Aveiro-Portugal	the missing resistor! No...its not! It need the resistor!

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5th March 2003, 12:51 AM	#3
martioz diyAudio Member Join Date: May 2002 Location: Melbourne	trying again... Edit: can't post attachment maybe link works: http://www4.head-fi.org/forums/attac...&postid=312006

5th March 2003, 07:36 AM	#4
phase_accurate diyAudio Member Join Date: May 2002 Location: Switzerland	Your outer loop generates positive feedback !! Regards Charles

5th March 2003, 08:56 AM	#5
Circlotron diyAudio Member Join Date: Jun 2002 Location: Melbourne, Australia	Yeah, two cascaded inverting amps make a non-inverting amp! Add a third stage. Other than that, you want to return R4 to the junction of R2 and R3.

5th March 2003, 11:24 PM	#6
martioz diyAudio Member Join Date: May 2002 Location: Melbourne	Thanks for pointing this out; I was half asleep when I post it. I hope now the circuit is correct, the idea is to use two inverting opamps to get non-inverted signal. Get inner loops to stabilize opamps and outer loop to adjust required gain. Link: http://www4.head-fi.org/forums/attac...&postid=312845 But I think, since this circuit is to be used as a "gain clone", let’s say gain about 100, the function of the outer loop losing functionality.

6th March 2003, 12:15 AM	#7
martioz diyAudio Member Join Date: May 2002 Location: Melbourne	Corrected Attachment (Link): http://www4.head-fi.org/forums/attac...&postid=312898

6th March 2003, 12:48 AM	#8
Circlotron diyAudio Member Join Date: Jun 2002 Location: Melbourne, Australia	Every connection to U1 pin 2 needs a resistor in series. The top opamp output hasn't got one in series with it's output to U1 pin 2 like it should.

6th March 2003, 01:31 AM	#9
martioz diyAudio Member Join Date: May 2002 Location: Melbourne	Is it better to return signal from the output of the feedback opamp to the point in front of R2 instead of adding extra resistor to the global loop?

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