OK a quick search seems to confirm the issue, but at high frequencies sometimes and with some resistors. Zfoils for instance it would be UHF. but thick film, we could see some effects on GBWP...maybe...
a thread on edaboard.com (good forum) had this to say in response to
this question
a thread on edaboard.com (good forum) had this to say in response to
this question
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Why not? Some of my resistors have 1 inch by 4 inch lead cross sections, or about 4000 kcmil..
And that's only for my preamp...
What a crazy Q and A..
11 amps into a milliohm, 11 millivolts..
The current derivative is 11 times 50,000 times 6.28, or ~ 3.3 million amps/sec..
L dI/dt = V..
1 henry inductance = 3.3 million volts.
1 mH =3,300 volts
1 uH =3.3 volts
1 nH =3.3 mV.
So a 30 % error would be had with a 1nH resistor.
Um, wonder what he ended up doin??
jn
Yes Scott too much alcohol, and completely switching 2nd & 3rd.
Thin film resistors run around 1000 Angstrom's in coating thickness. My back of envelope calculation says anything thinner than .005" should be okay for audio.
Of course I mixed the units, now we can see who can follow what that means!
Dick,
Would you quite giving away secrets that I charge to tell John!
ES
Thin film resistors run around 1000 Angstrom's in coating thickness. My back of envelope calculation says anything thinner than .005" should be okay for audio.
Of course I mixed the units, now we can see who can follow what that means!
Dick,
Would you quite giving away secrets that I charge to tell John!
ES
skin/proximity effects themselves are linear phenomena
if the current concentration causes higher local heating then a nonlinearity like TC may be exaggerated - a very 2nd order effect if the TC is already acceptably low, skin/proximity current crowding/impedance change only begins to be visiblea at few % at highest audio frequencies in most audio circuit components
but skin/proximity effects in perfectly linear materials should only give "funny looking" impedance change with a fractional power dependence on frequency
if the current concentration causes higher local heating then a nonlinearity like TC may be exaggerated - a very 2nd order effect if the TC is already acceptably low, skin/proximity current crowding/impedance change only begins to be visiblea at few % at highest audio frequencies in most audio circuit components
but skin/proximity effects in perfectly linear materials should only give "funny looking" impedance change with a fractional power dependence on frequency
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jn:
oh haha yeah I just skimmed his question just a quick well chosen google term got me there and I like that forum, dpont know what he did actually, but rather than theorizing further about it as i'm about to hit the bed, there is this link, which looks to be about as good an answer as we are going to get.
it was linked by one of the replies and includes thermal imaging pictures of high power chip resistors and a graph vs F as well as all the math we could ask for. more than I asked for I can tell you with the state of my head
I wasnt thinking of him actually meaning he had 11A measured across the mohm just that there was 11A being fed to the circuit, thats crazy alright! lol
oh haha yeah I just skimmed his question just a quick well chosen google term got me there and I like that forum, dpont know what he did actually, but rather than theorizing further about it as i'm about to hit the bed, there is this link, which looks to be about as good an answer as we are going to get.
it was linked by one of the replies and includes thermal imaging pictures of high power chip resistors and a graph vs F as well as all the math we could ask for. more than I asked for I can tell you with the state of my head
I wasnt thinking of him actually meaning he had 11A measured across the mohm just that there was 11A being fed to the circuit, thats crazy alright! lol
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I could.
Thick film might be 0.0005" or a bit less. Deposited vapor for thin film will be ten times lower. Resistivities will be several orders of magnitude lower than copper. Bulk foil drops midway between thick film and thin film. So you have both things (geometry and conductivity) working against any significance to skinning in ordinary film resistors or expensive thick film.
yeah well we pretty much came to that conclusion a while ago yes, but still worth following it through to find what resistance, what effect, what frequency. I thought it was interesting anyway and that document I found and linked from AT ceramics high power resistive products, 'Design, Test and Measurement, Performance and Mounting' looks excellent reading so its been downloaded for later
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To the best of my knowledge, skin effect does not normally cause any nonlinear distortion, just a roll-off approximating 3dB/oct. The only REAL problem with small amounts of 'skin effect' was brought forth by Dr. M. Hawksford in his wire articles, and here it DID create a non-linear time displacement that JN has hooted down as virtually impossible.
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I could.
Ah, so pray tell..how will it fare with proximity effects? That unfortunately, has nothing to do with the thickness of the film...and is actually the test I asked Ed about trying.
jn
Actually, Dr. Hawksford forgot about the permeability of the magnetic steel wires he used, there was an inductance of 15 nh per foot times times 100, or 1.5 uH per foot that he forgot to consider. So he concluded incorrectly.
I thought you understood that by now, so why in the world would you bring that dead horse up again?
jn
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