I miss measurements from dated and recent low cost op-amps like the 4558 or the LM833/LM837 in this study. I like low-cost good performers.
It's a great work otherwise, particularly because it shows the actual shape and spectrum of the distortion residuals. This is great information for anybody willing to interpret it.
It's a great work otherwise, particularly because it shows the actual shape and spectrum of the distortion residuals. This is great information for anybody willing to interpret it.
Thank you Mr. John Curl.
I am sorry to invade your rigth not to answer those things when asked.
But it is on time to me.... was just a small delay into the answer.
thank you and i apologize to invade your rigths.
regards,
Carlos
............................................................................................................
Thanks to you also Eva, your opinion is a nice contribution to my question.
You're also very respectable person that has a lot of knowledge.
Gracias,
Carlos
I am sorry to invade your rigth not to answer those things when asked.
But it is on time to me.... was just a small delay into the answer.
thank you and i apologize to invade your rigths.
regards,
Carlos
............................................................................................................
Thanks to you also Eva, your opinion is a nice contribution to my question.
You're also very respectable person that has a lot of knowledge.
Gracias,
Carlos
Carlos, I have answered you the best way that I can. I really don't have any absolute opinions on this subject. The biggest problem with IC's, in my opinion, is that they tend to starve the output stage in order to save current, and this causes higher order distortion to be generated. ALL my discrete preamp circuits operate in class A, and don't have this problem.
Yes... i see this as a limiting factor too...operating AB to allow low current
and small heat.... also small distance from input to output... because some chip, same die. (good for thermal control purposes)
Thank you... i am satisfied with your attention and i could understand a lot of things.... even the slow gap of time to answer, the small delay, made me realise a lot of things.
Really i am feeling gratefull.
regards,
Carlos
and small heat.... also small distance from input to output... because some chip, same die. (good for thermal control purposes)
Thank you... i am satisfied with your attention and i could understand a lot of things.... even the slow gap of time to answer, the small delay, made me realise a lot of things.
Really i am feeling gratefull.
regards,
Carlos
John, you are right about the output stages. As Scott remarked on another thread, mos t linear systems designers (i.e. the guys who do the industrial, power, scientific stuff etc) place high value on moderate power consumption. Unfortunately, its the o/p stage as you point out that gets compromised. It was suggested that a bias pin be brought out that would allow the user to set the o/p bias to a higher value, but this is a no go (Scotts Feedback).
Only other option is to load the output into class A ans buffer it with some discrete circuit like a diamond buffer. This takes advantage of the generally good front ends in a lot of the better op-amps.
Looks like we cannot have our cake and eat it.
Only other option is to load the output into class A ans buffer it with some discrete circuit like a diamond buffer. This takes advantage of the generally good front ends in a lot of the better op-amps.
Looks like we cannot have our cake and eat it.
Scott Wurcer,
---Someone here was building one, they emailed me a schematic.---
Darkfenriz
---I've one used bootstraped current mirror but rather a different way in a power amp. What kind of info do you need?---
Hi,
Schematics are wellcome. I am always interested in the practical implemention and the results (performances, reliability) of a new idea (at least to me). It's the first time I see a bootstrapped current mirror, I wonder how it behaves compared to other sophisticated schemes such as cascoded current mirrors.
---Someone here was building one, they emailed me a schematic.---
Darkfenriz
---I've one used bootstraped current mirror but rather a different way in a power amp. What kind of info do you need?---
Hi,
Schematics are wellcome. I am always interested in the practical implemention and the results (performances, reliability) of a new idea (at least to me). It's the first time I see a bootstrapped current mirror, I wonder how it behaves compared to other sophisticated schemes such as cascoded current mirrors.
Amazing opamp measurement shoot-out:
http://recforums.prosoundweb.com/index.php/t/24704/0/
Any kind of shootout, will be biased in some way, by the intent, the hypothesis or desire of the investigator.
- selection of objects to test
- selection of parameters to test
- and parameters not to test
- selection of data presentation of test result
- the conclusive statement, opinion of the tester
Nevertheless, any such comparing test performed
can give us some useful additional knowledge and information.
So is very welcome
http://recforums.prosoundweb.com/index.php/t/24704/0/
Any kind of shootout, will be biased in some way, by the intent, the hypothesis or desire of the investigator.
- selection of objects to test
- selection of parameters to test
- and parameters not to test
- selection of data presentation of test result
- the conclusive statement, opinion of the tester
Nevertheless, any such comparing test performed
can give us some useful additional knowledge and information.
So is very welcome
Here is the PDF Document for download
Operational Amplifier Distortion
by Samuel Groner, 1 September 2008
http://www.sg-acoustics.ch/analogue_audio/ic_opamps/pdf/opamp_distortion.pdf
Operational Amplifier Distortion
by Samuel Groner, 1 September 2008
http://www.sg-acoustics.ch/analogue_audio/ic_opamps/pdf/opamp_distortion.pdf
Hello John
The THS4031 do have an higher bias (close to a class A) than most Ic.
For myself I allway use my Ic into class A with a resistor or a CCS from rail to ouput, but the THS4031 may not need it since its high bias.
Thank
Bye
Gaetan
At the risk of being run out of town, I keep coming back to the LF353
I have used several of the other amps including the LM4580.
The key I think is to use these op amps at high frequency gains less then 5
The phono stage uses a low noise bipolar front end (Av =20) overall s/n = 93db.
I noticed that this amp (LF358) had very linear distortion curves.
In practice , it is almost impossible to get them to oscillate with an appropriate output decoupling resistor.
The latest project has a LF353 a/d 1st stage in my 1.3 mhz class d amplifier
with spectacular results.
I have used several of the other amps including the LM4580.
The key I think is to use these op amps at high frequency gains less then 5
The phono stage uses a low noise bipolar front end (Av =20) overall s/n = 93db.
I noticed that this amp (LF358) had very linear distortion curves.
In practice , it is almost impossible to get them to oscillate with an appropriate output decoupling resistor.
The latest project has a LF353 a/d 1st stage in my 1.3 mhz class d amplifier
with spectacular results.
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