distortion with Class B (with NFB) vs Class AB

[JW]

On Thu, 29 May 2014 06:03:09 -0400 JW <none@dev.null> wrote in Message id:
<1b1eo9t4p3hdh2e2tm9o71q2iim8qi0vla@4ax.com>:

On Wed, 28 May 2014 16:27:39 -0500 Jurd
guitardorkspamspameggsandham74@gmail.com> wrote in Message id:
lm5kbm$fpj$1@news.albasani.net>:

On 5/28/2014 12:12 PM, mrdarrett@gmail.com wrote:
On Wednesday, May 28, 2014 2:30:52 AM UTC-7, jurb...@gmail.com wrote:
"Oh! How many watts are typically required for a rock concert?



Actually none.


Like this?

http://memeheroes.com/83e90-just-listening-to-some-rock/




Nothing like cute girls who listen to heavy rock.

Better yet, cute girls who play heavy metal.
https://www.youtube.com/results?search_query=meytal+cohen

Yum!

My favorite: https://www.youtube.com/watch?v=4Yw8aaqnnrg

 

On Thursday, May 29, 2014 3:06:25 AM UTC-7, JW wrote:

On Thu, 29 May 2014 06:03:09 -0400 JW <none@dev.null> wrote in Message id:

1b1eo9t4p3hdh2e2tm9o71q2iim8qi0vla@4ax.com>:



On Wed, 28 May 2014 16:27:39 -0500 Jurd

guitardorkspamspameggsandham74@gmail.com> wrote in Message id:

lm5kbm$fpj$1@news.albasani.net>:



On 5/28/2014 12:12 PM, mrdarrett@gmail.com wrote:

On Wednesday, May 28, 2014 2:30:52 AM UTC-7, jurb...@gmail.com wrote:

"Oh! How many watts are typically required for a rock concert?







Actually none.





Like this?



http://memeheroes.com/83e90-just-listening-to-some-rock/









Nothing like cute girls who listen to heavy rock.



Better yet, cute girls who play heavy metal.

https://www.youtube.com/results?search_query=meytal+cohen



Yum!



My favorite: https://www.youtube.com/watch?v=4Yw8aaqnnrg

Well there's something you don't see every day!

 

No, true class B has no bias, in tis, the bias is the normal quiescent current drain ot the IC. the E to B resistors set that bias, and tha tis not the best idea because quiescent current of an OP AMP IC might not be the most tightly controlled parameter of the device. Why would it be ? If it has a pushpuill output stage, then its bias comes into play, and if it si highter but withint limits, fine. If it is lower within limits fine.

I consider this design pretty much no good. Maybe good for cheapness, but, well, not even for a headphone amp. Piece of shit is what some would say. Others kust mean it.

If you could trim the internal bias of the OP AMP, maybe. People, evne if it has zero offset, that doesn't mean that if it is groumded anywhere that the current drain from the positive and negative rails is going to be equal.

Fact is, the whole design is so shitty I woulldn't even do it with discrete components. there are so many more ways. The problem is tha these websites and shit that supposedly teach you how to design do not. thewy teach you how to use ICs.

The IC designers are the omes who design, you jusr mount the tires. I can design the IC, in configuration. I canot do anything about the die, wich others can. I can give you an asskicking design for an OP AMP you do with four transistors and about six other components. Nothing with more than three temrinals.

Wanna see ?

 

[Bill Bowden]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:9772o9530jtjuouvs3emcl56og9e25bll5@4ax.com...

On Sat, 24 May 2014 09:44:01 -0700 (PDT), mrdarrett@gmail.com wrote:

On Saturday, May 24, 2014 8:04:38 AM UTC-7, Jim Thompson wrote:
On Fri, 23 May 2014 21:31:22 -0700, John Larkin

On Fri, 23 May 2014 20:34:00 -0700 (PDT), mrdarrett@gmail.com wrote:

Then take the feedback from the actual output, rather than from the
OpAmp.

I had a feeling that was part of my "homework" to make it "less horrible."
Michael

And then bias the transistors on some.

Why would you bias the transistors on? Seems the op-amp can handle the
current during the crossover period of maybe 10 millamps and generate a volt
across the 100 ohm resistors and turn on the boosters. Shouldn't this
circuit be a true class B with zero bias?




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[Jurd]

On 5/31/2014 11:46 PM, jurb6006@gmail.com wrote:

No, true class B has no bias, in tis, the bias is the normal quiescent current drain ot the IC. the E to B resistors set that bias, and tha tis not the best idea because quiescent current of an OP AMP IC might not be the most tightly controlled parameter of the device. Why would it be ? If it has a pushpuill output stage, then its bias comes into play, and if it si highter but withint limits, fine. If it is lower within limits fine.

I consider this design pretty much no good. Maybe good for cheapness, but, well, not even for a headphone amp. Piece of shit is what some would say. Others kust mean it.

If you could trim the internal bias of the OP AMP, maybe. People, evne if it has zero offset, that doesn't mean that if it is groumded anywhere that the current drain from the positive and negative rails is going to be equal.

Fact is, the whole design is so shitty I woulldn't even do it with discrete components. there are so many more ways. The problem is tha these websites and shit that supposedly teach you how to design do not. thewy teach you how to use ICs.

The IC designers are the omes who design, you jusr mount the tires. I can design the IC, in configuration. I canot do anything about the die, wich others can. I can give you an asskicking design for an OP AMP you do with four transistors and about six other components. Nothing with more than three temrinals.

Wanna see ?

Sure.

-J

 

[Bill Bowden]

On Saturday, May 31, 2014 9:46:12 PM UTC-7, jurb...@gmail.com wrote:

No, true class B has no bias, in tis, the bias is the normal quiescent current drain ot the IC. the E to B resistors set that bias, and tha tis not the best idea because quiescent current of an OP AMP IC might not be the most tightly controlled parameter of the device. Why would it be ? If it has a pushpuill output stage, then its bias comes into play, and if it si highter but withint limits, fine. If it is lower within limits fine.



I consider this design pretty much no good. Maybe good for cheapness, but, well, not even for a headphone amp. Piece of shit is what some would say. Others kust mean it.



If you could trim the internal bias of the OP AMP, maybe. People, evne if it has zero offset, that doesn't mean that if it is groumded anywhere that the current drain from the positive and negative rails is going to be equal.



Fact is, the whole design is so shitty I woulldn't even do it with discrete components. there are so many more ways. The problem is tha these websites and shit that supposedly teach you how to design do not. thewy teach you how to use ICs.



The IC designers are the omes who design, you jusr mount the tires. I can design the IC, in configuration. I canot do anything about the die, wich others can. I can give you an asskicking design for an OP AMP you do with four transistors and about six other components. Nothing with more than three temrinals.



Wanna see ?

Sure, I wanna see. But I still don't see why the transistors need to be biased on (collector current flowing). From the spec sheet, the op-amp supply current varies from 4 to 8mA which yields 400 to 800 millivolts across the E/B 100 ohm resistors and may or may not turn on the transistors. Why not trim the E/B resistors to maybe 50 ohms so the E/B voltage is half that and the transistors are definitely off (no collector current)? And at say 15 milliamps of op-amp load current, the E/B voltage is 0.75 which is enough to turn on the transistor before the op-amp runs out of gas. Wouldn't that be better for thermal runaway problems?