Attachments
That one looks complicated enough to be very precise, jam 
Below are the 'LTP' Current Mirrors used in CA3080 by Intersil.
The operational transconductance amplifier (OTA) CA3080 needs very good mirrors to perform well.
For D3 in schematic should be used transistor in diode mode.
D2 and D4 are so called 'speed up diodes'.
They are attached backwards from current flow.
The Mirrors output uses two transistors in Darlington.
Litterature: CA3080 PDF from Intersil
Below are the 'LTP' Current Mirrors used in CA3080 by Intersil.
The operational transconductance amplifier (OTA) CA3080 needs very good mirrors to perform well.
For D3 in schematic should be used transistor in diode mode.
D2 and D4 are so called 'speed up diodes'.
They are attached backwards from current flow.
The Mirrors output uses two transistors in Darlington.
Litterature: CA3080 PDF from Intersil
Attachments
homemodder,
I started collecting these years ago when I was on the hunt for a mirror that was better than the basic Widlar (which I consider marginal at best).
I think we can safely say that we has seemed to have narrowed it down to three topologies though the Nakamura above might be worth investigating.
More stuff to drive you crazy....
http://www.google.com/patents?id=ev...537&source=gbs_selected_pages&cad=1_1#PPA1,M1
http://www.google.com/patents?id=fX02AAAAEBAJ&printsec=abstract&zoom=4&dq=5283537#PPA1,M1
................and one for the totally insane.
http://www.google.com/patents?id=MRMwAAAAEBAJ&printsec=abstract&zoom=4&dq=5283537
Regards
Jam
I started collecting these years ago when I was on the hunt for a mirror that was better than the basic Widlar (which I consider marginal at best).
I think we can safely say that we has seemed to have narrowed it down to three topologies though the Nakamura above might be worth investigating.
More stuff to drive you crazy....
http://www.google.com/patents?id=ev...537&source=gbs_selected_pages&cad=1_1#PPA1,M1
http://www.google.com/patents?id=fX02AAAAEBAJ&printsec=abstract&zoom=4&dq=5283537#PPA1,M1
................and one for the totally insane.
http://www.google.com/patents?id=MRMwAAAAEBAJ&printsec=abstract&zoom=4&dq=5283537
Regards
Jam
Current mirror performance has zilch to do with input stage linearity in a competent design - although the input offset adjustment idea is nice.
And by "competent design" I don't mean an early 1970s HK Citation clone that some hack treats like it's his intellectual property.
In a competent design with emitter degeneration of the input stage, power amp input stage distortion at full power, 20 kHz, can be improved by a factor of 10 or more without messing with the mirror at all. Just do a bootstrapped cascode a la Widlar's design of the LM108.
And by "competent design" I don't mean an early 1970s HK Citation clone that some hack treats like it's his intellectual property.
In a competent design with emitter degeneration of the input stage, power amp input stage distortion at full power, 20 kHz, can be improved by a factor of 10 or more without messing with the mirror at all. Just do a bootstrapped cascode a la Widlar's design of the LM108.
No Im not wrong, you are not a psyciatrist, you have no psycology training and therefore no merit to make such a judgement or evaluation and nor do I, but at least I asked someone who does, her thoughts about this.
Nobody has reached consensus, and so far everyone has said it has to be tested and listening evaluations done. Ostripper has done his evaluation but nobody else has so far. There are some agreements and some disagreements, input from from others are considered, no it doesnt fit the all the criteria.
Not perfect but maybe better suited for what we want to use them for. MJL21193 werent you also trying this and that to address issues you had with your amp and evaluating cons and pros, same is happening here on this thread. Its not about the perfect current mirror in so much, but how it affects the surrounding circuitry. Maybe you think its futile, same some members though it futile for you achieve lower THD or better squarewave response but this was important in your view while not shared by everyone else. Perfection doesnt exist in electronics and I doubt in anything else. No need to come critisize people here for evaluating current mirrors rather contribute something usefull or share your thoughts even if its that you think it futile but then say so and state your reasons and put them up for scrutiny.
Imagine where audio, lets rather say Lin topology would be, if designers like Self didnt investigate his theories and compare with other designers. And yes he discusses them too, takes note of others opinions and gets new ideas, go over to thermaltrak thread as an example and see for yourself. This is not groupthinking, its called discussion.
Glen, why not go over to that thread and call it groupthink to those involved there, in fact one could classify 70 percent of the threads to groupthink then taking into account your interpretation of the term.
Anyway thats it about groupthink, this is a audio forum not a psycology forum so for those interested in the subject there are some psycology forums around for the purpose. Please feel free to come and copy whole thread here for evaluation on said forums but no need to place findings here as they are of no relevance or interest and even less so when composed by unqualified and non experienced people in this field.
Nobody has reached consensus, and so far everyone has said it has to be tested and listening evaluations done. Ostripper has done his evaluation but nobody else has so far. There are some agreements and some disagreements, input from from others are considered, no it doesnt fit the all the criteria.
Not perfect but maybe better suited for what we want to use them for. MJL21193 werent you also trying this and that to address issues you had with your amp and evaluating cons and pros, same is happening here on this thread. Its not about the perfect current mirror in so much, but how it affects the surrounding circuitry. Maybe you think its futile, same some members though it futile for you achieve lower THD or better squarewave response but this was important in your view while not shared by everyone else. Perfection doesnt exist in electronics and I doubt in anything else. No need to come critisize people here for evaluating current mirrors rather contribute something usefull or share your thoughts even if its that you think it futile but then say so and state your reasons and put them up for scrutiny.
Imagine where audio, lets rather say Lin topology would be, if designers like Self didnt investigate his theories and compare with other designers. And yes he discusses them too, takes note of others opinions and gets new ideas, go over to thermaltrak thread as an example and see for yourself. This is not groupthinking, its called discussion.
Glen, why not go over to that thread and call it groupthink to those involved there, in fact one could classify 70 percent of the threads to groupthink then taking into account your interpretation of the term.
Anyway thats it about groupthink, this is a audio forum not a psycology forum so for those interested in the subject there are some psycology forums around for the purpose. Please feel free to come and copy whole thread here for evaluation on said forums but no need to place findings here as they are of no relevance or interest and even less so when composed by unqualified and non experienced people in this field.
homemodder said:
That should read "in fact one could classify 70 percent of the threads to groupthink then taking into account my interpretation of your interpretation of the term".
Also, I don't need to be a psychiatrist to have an opinion with respect to the plausibility of much of the subjectivist claims made around here.
Strewth Glen, can you please give it a rest ... the thread it not "groupthink", it is "Current Mirrors" and if you unhappy with Hugh (and visa-verse) please (both of you) take it off-line.
Also, if none of the other CM's that have been mentioned are any good, other than the 3T version that you have mentioned, please tell us why.
We know that you are very knowledgeable, so, please espouse your knowledge. Facetiousness is not an expression of knowledge ...
anyway, try and have a good day
Also, if none of the other CM's that have been mentioned are any good, other than the 3T version that you have mentioned, please tell us why.
We know that you are very knowledgeable, so, please espouse your knowledge. Facetiousness is not an expression of knowledge ...
anyway, try and have a good day
Hi, everyone . I am finally bold enough to create the "frugalamp"
thread.(you will see in 1 hour) The amp (with mods) successfully
drove a real speaker today. now the only problem is the
speakers as they can not handle that many "fat electrons"
(over excursion is too easy - speakers are only 120w.)
This thread 's timing was most timely, as I was actually
building at the time,.. thanks to all.
What design ??
OS
andy_c said:
thanks, andy_c
Bob Widlar has given name to among other things, one current mirror.
Bob Widlar uses no mirror in input stage of LM108 (1969).
See attachment.
This is a very low supply current opamp, 300uA !!! ( 0.3mA ).
Using super beta input transistor pair, which needs to be cascoded.
I find LM108 to be an elegant amplifier
Lineup
Attachments
Glenthink or Groupthink?
I hope this thread does not degenerate into a flamewar.
Maybe the Groupthink movement should have it's own thread. Glen might have a valid point but I don't think it is helping this thread.
To those of you that don't see the importance of a better mirror, let me put it to you this way. In my experience, any little improvement helps and the total of all these little improvements can be huge. Assuming tht feedback is going to correct everything is blatently false.
Please correct me if I am wrong, but shouldn't every part of an amplifier be designed to be as linear as possible before the application of feedback? The distortion measurements might be the same but they usually do not sound the same. This happens to be the case in the difference of the two and three transistor versions of the Widlar. I should think in a non-loop feedback circuit this might be more important.
That being said, has anyone any comments on the Nakamura Mirror?
Jam
I hope this thread does not degenerate into a flamewar.
Maybe the Groupthink movement should have it's own thread. Glen might have a valid point but I don't think it is helping this thread.
To those of you that don't see the importance of a better mirror, let me put it to you this way. In my experience, any little improvement helps and the total of all these little improvements can be huge. Assuming tht feedback is going to correct everything is blatently false.
Please correct me if I am wrong, but shouldn't every part of an amplifier be designed to be as linear as possible before the application of feedback? The distortion measurements might be the same but they usually do not sound the same. This happens to be the case in the difference of the two and three transistor versions of the Widlar. I should think in a non-loop feedback circuit this might be more important.
That being said, has anyone any comments on the Nakamura Mirror?
Jam
Re: Glenthink or Groupthink?
1. FYI, distortions are adding squarely. So, if stage A has 0.005% and stage B has 0.01%, the combination will have 0.011%. As you see, 50% less in the first stage distortions gets you only a 10% change in the total.
2. Exactly so, but that's not necessary because of a change in THD.
3. Prove it.
jam said:
1. FYI, distortions are adding squarely. So, if stage A has 0.005% and stage B has 0.01%, the combination will have 0.011%. As you see, 50% less in the first stage distortions gets you only a 10% change in the total.
2. Exactly so, but that's not necessary because of a change in THD.
3. Prove it.
syn08.
You seem to be one of those meter men.
1. Your assumption is all types of distortion sound the same.
2. The distribution or harmoinc content might be different.
3, I have tried it why don't you. Several other members seem to concur, including Glen. There are fundamental problems with the two transistor mirror, Mr.Google might help you here.
Is this an excersise in if you can't measure it , you can't hear it or are you more interested in displaying your credentials. So I leave it up to you to prove me wrong
I suggest you build a circuit and graft in the changes and prove it to yourself or not.
Warmest regards, (and I mean it)
Jam
You seem to be one of those meter men.
1. Your assumption is all types of distortion sound the same.
2. The distribution or harmoinc content might be different.
3, I have tried it why don't you. Several other members seem to concur, including Glen. There are fundamental problems with the two transistor mirror, Mr.Google might help you here.
Is this an excersise in if you can't measure it , you can't hear it or are you more interested in displaying your credentials. So I leave it up to you to prove me wrong
I suggest you build a circuit and graft in the changes and prove it to yourself or not.
Warmest regards, (and I mean it)
Jam