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Old 10th January 2013, 06:18 PM   #32471
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Quote:
Originally Posted by gpapag View Post
Thank you Ed.
The 1.414 multiplier on second column fell into the glass of Ouzo and lost itís senses.
I attach the corrected table.



From here,
http://www.ti.com/lit/ds/symlink/lm4562.pdf

distortion is listed as 0.00003% -0.00009% (5th decimal place) at 4V out, 600-10KOhm load and the measurement is conducted with a 1K Rf (see Fig.4 for the trick used to measure such low distortion), thus this figure should logically include the distortion produced due to Rf.

Apart from this, how do you perform the resistor distortion calculations?

George
George,

I have looked at how they do the distortion measurements and I think they are in error! I think most of what they are seeing is still from the resistors.

I assume you understand my 10 resistor method to measure the distortion. From there it is 3 db more per octave of lower frequency for the third harmonic and 6 db more for each doubling of voltage. Straight power law!

As I test at 1000 Hz the distortion goes up by 10 db at 100 Hz and if for some reason you want to use 20 Hz add another 7 db. My test voltage is 7 volts. The other factor is since I am comparing the resistor to identical units at 1/2 power you must add another 3-6 db for the uneven voltage divider effect. And as I have mentioned if you use the other resistor in the divider with a different thermal time constant you can add another 50 dB for the music to ear compensation!

So enjoy the Ouzo. Also note almost no one else even understands what we have been discussing!
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Old 10th January 2013, 06:52 PM   #32472
marce is offline marce  United Kingdom
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useless information #2:
a bit more on skin effect in PCB traces, the ground proximity effect further down is quite interesting:
Printed Circuit Design & Fab Magazine Online
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Old 10th January 2013, 06:54 PM   #32473
DF96 is offline DF96  England
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Quote:
Originally Posted by RNMarsh
These things matter in high current, fast rise pulse fidelity.
We just have to be careful to remember that lack of 'pulse fidelity' is not the same as non-linear distortion. A linear filter can change pulse shape.
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Old 10th January 2013, 06:59 PM   #32474
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Proximity effect is not linear. Why is that being assumed???

When the current in the lead is causing proximity dependent current redistribution, the equation is of the form:

effect = K(onstant) times (dI/dt)squared.

When the current is rising positive, the current profile of the the cylindrical resistor current will try to take the lowest impedance path, which is as close to the outside lead near the body as the current can to.

When the current is falling negative, the current profile of the the cylindrical resistor current will try to take the lowest impedance path, which is as close to the outside lead near the body as the current can to.

Note that no matter which way the current is changing, the end effect is the current will redistribute in the same direction. The faster the absolute value of the slew, the higher the resistance...



Quote:
Originally Posted by jcx View Post
my very simplified model of a lumped "proximity effect" simulation
Nice model. However, there is no good way to simulate a field modified resistance. You can include inductive coupling, but not the variation of resistance with slew rate. And, see above, you need some ideal rectifiers in there.
Quote:
Originally Posted by RNMarsh View Post
useless information dept --> skin effect of circular conductors has the inductance lowest at or near the surface for HF. Thus, those currents flow or are denser there.
Agreed. And, there is no internal magnetic field with a cylindrical sheet of current.

However, that has nothing to do with the proximity effect I speak of..

Perhaps over the weekend Ed can try.

jn

Last edited by jneutron; 10th January 2013 at 07:19 PM.
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Old 10th January 2013, 07:04 PM   #32475
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Quote:
Originally Posted by marce View Post
useless information #2:
a bit more on skin effect in PCB traces, the ground proximity effect further down is quite interesting:
Printed Circuit Design & Fab Magazine Online

THANK YOU.

Everybody look at figure 3.

edit: Two other notes.

1. The author invokes HoJo. In his book, I think it was the '94 edition of high speed signal..., he intro'd a picture depicting the toroidal current loops which are cause by the inner magnetic fields of the conductor during current slew. At DC, the internal magnetic field is zero at center, and rises linearly to peak at conductor surface. During slew, this internal field creates the toroidal currents which are of a sign such that at the center it opposes bulk current flow, and enhances the outer surface bulk flow. I introduced this depiction back in '92 on some site, I think it was AH..

2. Figure 5 depicts the skin resistance in the T-line model as a simple resistor. It is in fact a time dependent resistor, depending on slew rate at any instant in time. A simple resistance is an approximation, as the actual value would be an extremely difficult one to use.

Last edited by jneutron; 10th January 2013 at 07:27 PM.
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Old 10th January 2013, 07:20 PM   #32476
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Quote:
Originally Posted by gpapag View Post
distortion is listed as 0.00003% -0.00009%
Thanks a lot, gpapag.
It means around -120/-130db... hum...
Since two days i was not sleeping by night, because all those nightmares of horrible distortions...
I will sleep tonight and dream of pink resistances...
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Old 10th January 2013, 07:31 PM   #32477
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Quote:
Originally Posted by simon7000 View Post
George,

I have looked at how they do the distortion measurements and I think they are in error! I think most of what they are seeing is still from the resistors.

!

Excuse me, these numbers are at G = <PLUS>1, the distortion making resistors must be imaginary. There is no current flowing in Rf in figure 4 save the (101x the error signal)/Rf. Come on guys, pay attention. Ed you mis-understood my joke, you said the thermal distortion was third order for a DRY resistor.
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Last edited by scott wurcer; 10th January 2013 at 07:38 PM.
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Old 10th January 2013, 07:36 PM   #32478
RNMarsh is online now RNMarsh  United States
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Quote:
Originally Posted by DF96 View Post
We just have to be careful to remember that lack of 'pulse fidelity' is not the same as non-linear distortion. A linear filter can change pulse shape.
generally true but only for a certain set of conditions. The delay caused by skin effect between low and high freq contained in a data pulse causes trouble with waveform shape which affects the data flow integrety. Timing circuits as well. Group delay and perhaps jitter as well [indirectly]. We arent living in just an analog music world.... well maybe we are in this thread. Thx-RNMarsh
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Old 10th January 2013, 07:40 PM   #32479
RNMarsh is online now RNMarsh  United States
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Quote:
Originally Posted by marce View Post
useless information #2:
a bit more on skin effect in PCB traces, the ground proximity effect further down is quite interesting:
Printed Circuit Design & Fab Magazine Online
Note I was careful to say - on a single pcb trace. That means without ground planes... which distributes the skin effect differently. But edges and sharp corner affects are still in affect. Thx-RNmarsh

Last edited by RNMarsh; 10th January 2013 at 07:42 PM.
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Old 10th January 2013, 07:48 PM   #32480
DF96 is offline DF96  England
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Quote:
Originally Posted by jneutron
Proximity effect is not linear. Why is that being assumed???
Proximity effect is just the mutual version of skin effect (i.e. self-proximity). Skin effect is linear, therefore proximity effect is too.

Quote:
Originally Posted by RNMarsh
generally true but only for a certain set of conditions.
We seem to be getting dangerously close to YAFD.
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