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Old 6th September 2012, 06:27 PM   #771
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by homemodder View Post
One can say the same for the circuit you published in TAA, JLH published the original idea back in 1968 although he did use resistors and not ccs.
JLH didnt invent that biasing form nor feedback scheme either... used in tube circuits long, long before then. I was just pointing out that the bias scheme was used by myself earlier than was noted ... not that I invented it. I was applying it to a different topology.

[If you dont understand the significant differences of the two topologies, there are plenty of books about the circuit and how it would differe from JLH design. One is: Emerging Techniques for High Freq BJT Amplifier design: A Current-Mode Perspective (1994) by C.Toumazou, J.Lidgey, A.Payne. Covers it so well, its in my reference library I keep. [ International Conference on Electronics Circuits and Systems, Cairo, Egypt.] But there are more contemporary books. -RNM

Last edited by RNMarsh; 6th September 2012 at 06:52 PM.
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Old 6th September 2012, 07:01 PM   #772
gpapag is offline gpapag  Greece
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Originally Posted by jneutron View Post
Here's a helpful guide:
http://www.lakeshore.com/Documents/LSTC_appendixC_l.pdf
Here's calibration stuff.

jn
This one helped me undertand the “thermal anchoring”. Very useful concept.

Talking about heat transfer, here is the useless information of the day

Quote:
The solder/copper interfacial thermal resistance (ITR) is on average about 0.020 K·cm2· W−1.
International Journal of Thermophysics, Volume 26, Number 5 - SpringerLink


I am googling myself on the copper/solder thermo EMF but I can’t find any numbers yet.

George
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Old 6th September 2012, 07:27 PM   #773
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Quote:
Originally Posted by gpapag View Post
This one helped me undertand the “thermal anchoring”. Very useful concept.

Talking about heat transfer, here is the useless information of the day


International Journal of Thermophysics, Volume 26, Number 5 - SpringerLink


I am googling myself on the copper/solder thermo EMF but I can’t find any numbers yet.

George
Thanks for the link, interesting read. the number, if they did it correctly, is certainly a useful one.

I must note:
1. They clearly don't solder for a living. They had to use a SAM to figure out they had voids??? Duh... Without weep or blow holes to clear flux and outgassing, what did they expect???
2. They consider the solder to copper interface as one entity? They don't realize that it is comprised of three layers? Two copper/tin intermetallic layers and then a pure solder layer lightly lead rich due to tin loss to the intermetallic formation??
3. Bet they didn't test the surfaces for solderability. They've probably no idea what percentage of the surface of the copper passivated with no metallic connection.
4. Their test technique is great when the thermal interface material is an order of magitude (or more) higher in thermal resistance than copper, as it produces a more isothermal secondary plate response. High conductivity interfaces such as solders tend to cause surface gradients on the secondary plate, remember it's a bounded geometry with edge causing specific heat discontinuty.

Soldering is a TWO THOUSAND year old technology. Still, mistakes are made..sigh.

I loved this gem:

""The density values were obtained by the
Archimedes’ method.""

No, tell me it ain't so. They displaced water to find the volume to calculate density? They used a rectangular cylinder of a known thickness, diameter, and weight, and couldn't calculate it's volume???? Shirley they jest...

But fun read. I would have checked the box "suitable for publication with revision".

jn
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Old 6th September 2012, 07:43 PM   #774
RNMarsh is offline RNMarsh  United States
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Soldering is a process of alloying metals. Might find more info of your interest via Googling on alloying.
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Old 6th September 2012, 07:58 PM   #775
bcarso is offline bcarso  United States
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Originally Posted by jneutron View Post
Soldering is a TWO THOUSAND year old technology. Still, mistakes are made..sigh.
LHC
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Old 6th September 2012, 08:08 PM   #776
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Originally Posted by RNMarsh View Post
Soldering is a process of alloying metals. Might find more info of your interest via Googling on alloying.
Yup. There's lots out there. I was tempted to google to get the copper tin ratios, but decided it wasn't worth it.

For tin/lead, the web has lots. For tin/silver, it's not as good out there as in house..

Problem with the web, is most do not have the understanding to be able to discern basic problems with what was written..the article linked being a good case in point. Most people won't even understand what I wrote, nevermind have the theoretical and practical underpinnings to figure out the article errors.

jn
R...I may have assumed incorrectly that you were speaking to me...if so....nevermind....

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Old 6th September 2012, 08:11 PM   #777
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Originally Posted by bcarso View Post
LHC
You got that right. They were TAUGHT about 15 years ago. I'd like to say ""did they listen...nooooo"", but that would be a cheap shot.. Personnel turnaround there played a large role in the explosion..those who were taught were not the ones who did. The information given them did not transfer during the personnel shuffles.

jn
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Old 6th September 2012, 08:36 PM   #778
RNMarsh is offline RNMarsh  United States
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It seems to me -- as a bonified old geezer now -- from hindsight - or the view from the bridge of my nose --> There is a lot of attention paid when something is new.... then it becomes mainstream. then it becomes forgotten. Then finally, lost -- in that order. Today new to forgotten happens a lot faster when the new gets folded into sim software. After that the derivation et al is forgotten.. and then lost. -Dick

Last edited by RNMarsh; 6th September 2012 at 08:38 PM.
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Old 6th September 2012, 09:20 PM   #779
gpapag is offline gpapag  Greece
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Quote:
Originally Posted by jneutron View Post
I must note:
1
2.
3.
4.
I loved this gem:

But fun read

jn
Jeez, I only had access to the “Abstracts”

I’ll never confess to you the story of my life. You’ll nail me in a minute with a thousand nails

Quote:
Problem with the web, is most do not have the understanding to be able to discern basic problems with what was written.
True but this may be the case with books too. The difference is that through the web we (I) have easy untargeted access.


Quote:
Most people won't even understand what I wrote
Yes. And then here I come asking, putting you into the trouble to answer and kindly explain.


Quote:
nevermind have the theoretical and practical underpinnings to figure out the …
Since many years now I have happily accepted the fact that I know very few things. And I try to read new. This I enjoy a lot.

My embarrassment comes from finding out frequently, that the things I know, I have understood them wrong.

But in general, I try to think positive

Ian Dury - Hit Me With Your Rhythm Stick [Official Video] - YouTube


Quote:
Originally Posted by jneutron View Post
those who were taught were not the ones who did. The information given them did not transfer during the personnel shuffles.
jn
In aviation industry there is a "politically correct" masquerading heading for this kind of messy issues: Human Factors.

For many years now it has become a mandatory training for the licensed engineers. Most of the curriculum is based on the aftermaths of such stupid common everyday mistakes.


George
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Old 6th September 2012, 09:22 PM   #780
RNMarsh is offline RNMarsh  United States
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Default Thermal-electric effects in metals

Google for Seebeck effect; The Seebeck coefficient is a material property that depends on temperature (micro volts/ degree C.) From that, EMF can be found....
Some Seebeck coefficients are: copper to silver or gold = 0.5 uv/C; Copper - nickel = 10; Copper to KOVAR = 40.
Strange one is copper to copper is not = 0 [thermal gradients matter].

Also google Thermal EMF of Solders.

Last edited by RNMarsh; 6th September 2012 at 09:31 PM.
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