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Old 6th August 2013, 09:03 PM   #121
smms73 is offline smms73  Portugal
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I use the bob cordell method.

Ps: I can try to solve the problem... if you want, of course.
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Last edited by smms73; 6th August 2013 at 09:15 PM.
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Old 6th August 2013, 09:10 PM   #122
dadod is offline dadod  Croatia
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Quote:
Originally Posted by smms73 View Post
I use the bob cordell method.
You can't use Bob method here, it's not ordinary GNFB, use Thian probe or simple voltage probe as I used(good enough in this case). If you change resistors value or use inductor it will disrupt ODNF behavior.
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Old 6th August 2013, 09:45 PM   #123
smms73 is offline smms73  Portugal
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the Thian Probe is a very good method.
I will have a closer look.

But at first look it seems similar to a classic GNFB , with the difference that the discrete circuit is doing the voltage swing , which facilitates the work of the opamp (less distortion), that only has to output the error voltage .
It seems a good technique for nested feedback loops.
But as I said , have to take a better look.
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Old 6th August 2013, 09:56 PM   #124
smms73 is offline smms73  Portugal
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You are right , the cordell method does not work here.
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Old 7th August 2013, 12:30 AM   #125
smms73 is offline smms73  Portugal
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This feedback method can have very low distortion, and I think that it can be use in a class B power amplifier with good results.
Is this protected by a patent? who invented?

but this circuit have some points that needs to be improved.
the settling time of the circuit is very bad .
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File Type: png settling_time.png (67.0 KB, 174 views)
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Old 7th August 2013, 03:19 AM   #126
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Originally Posted by dadod View Post
Why it would be -12V, it will be just enough to set output DC close to zero.
Why? There is no feedback from output to that point.
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Old 7th August 2013, 05:30 AM   #127
dadod is offline dadod  Croatia
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Quote:
Originally Posted by smms73 View Post
This feedback method can have very low distortion, and I think that it can be use in a class B power amplifier with good results.
Is this protected by a patent? who invented?

but this circuit have some points that needs to be improved.
the settling time of the circuit is very bad .
Thanks for the simulation, probably it needs input lowpass filter.
Sorry, highpass filter!

Last edited by dadod; 7th August 2013 at 05:36 AM.
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Old 7th August 2013, 05:31 AM   #128
dadod is offline dadod  Croatia
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Originally Posted by cbdb View Post
Why? There is no feedback from output to that point.
Yes there it is, ODNF op amp. Try to simulate.
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Old 7th August 2013, 09:54 AM   #129
smms73 is offline smms73  Portugal
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In post #125 the simulation was made with a lt1007.

here is with the original lme49710. First picture with the ODNF, second with the normal feedback.
the resistor P1 (10k) is slowing the feedback action.

third picture is without global negative feedback.
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File Type: png odnf.png (70.8 KB, 160 views)
File Type: png normal_feedback.png (70.3 KB, 154 views)
File Type: png no_nfb.png (69.5 KB, 149 views)
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Old 7th August 2013, 10:17 AM   #130
dadod is offline dadod  Croatia
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Quote:
Originally Posted by smms73 View Post
In post #125 the simulation was made with a lt1007.

here is with the original lme49710. First picture with the ODNF, second with the normal feedback.
the resistor P1 (10k) is slowing the feedback action.

third picture is without global negative feedback.
What are you talking abouth here, what normal feedback??
In second case this is not any more my pre amp, you disconnected the gain block completely and op amp acts as the gain stage, please don't do that!!!
I am not sure you understood the main concept here.
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