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Old 6th June 2012, 03:48 PM   #23731
SY is offline SY  United States
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"Mundane" in the sense that there's no new physics there, this is an interesting effect from known and well-characterized factors, but not any kind of breakthrough or game-changer.

If the superluminal stuff had held up, we would have a LOT of interesting new physics to figure out. It didn't, ah well, we're a bit disappointed but that's how it goes. As for aether, I would quote Laplace: "Je n'ai pas besoin de cette hypothese."
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Old 6th June 2012, 04:16 PM   #23732
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Still nothing of substance from any of them .

Looks like next stop Nigeria for the leader of the pack, http://www.cheniere.org/correspondence/020209.htm
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Old 6th June 2012, 04:48 PM   #23733
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Scott
Thank you for the inside look.
If I would ask for your opinion as to why it is not performed on lower freq. Ics too? (Multiple choise question)
a. Negligible effects at these freq.
b. Effects are not that dramatic at these freq.
c. Effects are equally important but layout correction not feasible within IC size, due to large dimentions –length, height- required for lower freq.
d. None of the above. (Please elaborate in 20 words)


JC, KBK, jneutron, bcarso, simon, jcx, thanks for responding.

George
For old style chips with aluminum bonding pads on the top surface, the pads are connected to the leadframe terminals via a wirebond, either aluminum or gold. This wirebond is looped a bit so as to not touch the edge of the substrate in it's travel to the lead. Back in the 80's (IIRC) it was determined that the parasitic inductance of the wires (14 nH for some reason, comes to memory) significantly affected the speed that could be attained for all I/O lines of the chip. Also, two parallel wires can also crosstalk.

The basic issue was the slew rate of the current, how it coupled to neighbors, how it affected the speed of the signal, and for hot and ground runs, it can introduce unwanted ground or rail bounce.

At lower frequencies, the slews are not as bad, so the parasitic inductance doesn't have as great an effect.

Nowadays, the problems I see in things like the one chip amps, is the proximity the rail currents are to the input nodes. Any proximity coupling from either rail to that node can introduce error signals at the input pair, where gain is full.

For a one chip amp, I would make sure the supply rails have a common centroid...return, plus, and minus. See attached..a pic from 2006. Home made triaxial cable.
j
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Last edited by jneutron; 6th June 2012 at 05:10 PM.
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Old 6th June 2012, 05:58 PM   #23734
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For old style chips with aluminum bonding pads on the top surface, the pads are connected to the leadframe terminals via a wirebond, either aluminum or gold. This wirebond is looped a bit so as to not touch the edge of the substrate in it's travel to the lead. Back in the 80's (IIRC) it was determined that the parasitic inductance of the wires (14 nH for some reason, comes to memory) significantly affected the speed that could be attained for all I/O lines of the chip. Also, two parallel wires can also crosstalk.
The numbers are 5-10x less on todays SMT packages OTOH we are trying to make 10G TIA's. If you check the AD8010 datasheet you will see a bypassing scheme that was necessitated by bond wire mutuals, that gets pretty amazing diff gain and phase with lots of parallel video loads.
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Old 6th June 2012, 06:13 PM   #23735
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Nowadays, the problems I see in things like the one chip amps, is the proximity the rail currents are to the input nodes. Any proximity coupling from either rail to that node can introduce error signals at the input pair, where gain is full.

For a one chip amp, I would make sure the supply rails have a common centroid...return, plus, and minus. See attached..a pic from 2006. Home made triaxial cable.
j
Well, for my favorite chip amp, the TDA7294 (and its cousins), the guys at ST got that bit right, it seems. Also it has split power and preamp/driver supplies, another nice feature given the rather bad PSRR
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Old 6th June 2012, 06:13 PM   #23736
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See attached..a pic from 2006. Home made triaxial cable.
j
If you ever need any small quantities, let me know I still have scraps left over. Normally we get "Thick" triax on 3500' put ups for stadium use. Any length under 300' is scrap.

Although with the high price of scrap we actually are getting rid of some of it.

Today was a shipping day. Three crates for two speaker clusters went out. Attached picture!

Anyone have a contest for biggest loudspeaker?
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Old 6th June 2012, 06:22 PM   #23737
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Anyone have a contest for biggest loudspeaker?
I have pair of line arrays made of capsules from dynamic microphones, 16 in each.
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Old 6th June 2012, 06:30 PM   #23738
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I have pair of line arrays made of capsules from dynamic microphones, 16 in each.
Is that the ones I heard at your house? If so, they were surprisingly good.
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Old 6th June 2012, 06:33 PM   #23739
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"Mundane" in the sense that there's no new physics there, this is an interesting effect from known and well-characterized factors, but not any kind of breakthrough or game-changer.
Thank you for explaining.

Quote:
Originally Posted by SY View Post
If the superluminal stuff had held up, we would have a LOT of interesting new physics to figure out. It didn't, ah well, we're a bit disappointed but that's how it goes.

Don’t give up hope (*). There may come one day…
Old stuff are like old men, stubborn. They refuse to give up.

http://maxwell.byu.edu/~spencerr/phys442/history.pdf


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As for aether, I would quote Laplace: "Je n'ai pas besoin de cette hypothese."
Well Messier SY, here is Lagrange from the same episode (**): “Ah! c'est une belle hypothèse; ça explique beaucoup de choses.”

George

(*)I know you are dying for a new “tongue test”

(**)Talk about God existence (hypothesis)
Besides, both men were long dead by the time things were becoming hot with aether-based valid electromagnetic theories.
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Old 6th June 2012, 06:44 PM   #23740
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Don’t give up hope (*). There may come one day…
I sure hope so. There's so much of the universe to explore and waiting millions of years for answers is not an attractive prospect.
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