It wouldn't take a big heat sink on top to seriously increase the surface area. On the bottom, one could extend the collector contact into a pour, around and under the part. No solder mask underneath. Maybe a dab of epoxy to close the air gap.
To measure that, I guess I'd have to use the pulsed Vbe trick, to get the actual junction temperature. Grounded-base maybe. Sounds like fun.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Build a Farnsworth fusor, and chase after the neutrons until they decay? :-)
Yeah, most likely. Some sort of electron bombardment thing. Not sure if it's a feasible goal to have a fairly high density of low velocity (space charge) protons coming out of such a mess. For sure, you can't have them in equilibrium with a metal, as you can with electrons.
Well...
What if you did nickel or palladium nanowires doped with hydrogen? With field emission, would you get protons -- freed at fairly low "work potential"?
That would of course be even less effective or reliable than electron field emitters, unless proton diffusion through those materials is much faster than I imagine. I don't know that field emission can ever have as low noise as non-saturated thermionic emission can.
It's chemically weird, because protons are literally the most acidic thing that can be conjured (pure Bronsted-Lowry acid incarnate). Hard to do that without screwing up the rest of the, erm, anti-cathode.
Hmm... lots of possibilities, at least.
That would definitely be part of the qualification: testing the noise level to verify that it's doing the physics that I think it is (or want it to be..).
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
That it's > 1.000 proves my point, so that's good enough for a pedant like me. :^)
It's actually slightly better than that even, if you go to higher and higher order networks.
Almost a half a decade -- it may not be duck liver, but chicken liver is nice in gravys.
Of course the tolerances quickly become preposterous, so you have little if any value in going beyond the 2nd order (T coil) case.
It's funny because, in the sorts of things we're talking, distributed networks -- transmission lines -- could be used for these networks. The matching could be etched into the PCB, to any order we desire. Solving for that pattern is, of course, nontrivial. :(
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Distributed amplifiers are cool. You break up your gain element into smaller chunks and string them down a transmission line.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Has anyone tried thermally conductive potting to kee Tj down ? We did some impressive tests for an Atex/IECEx design, like dissipating 6.5W from TSSOP8. Silicone based compound was also easy to pry off, unlike epoxy-based one.
-- mikko
About 0.3 sheep.
What kind of thermally conductive epoxy did you use?
--
Thanks,
- Win
of 8
er
There's a theorem of Bode's to the effect that if you start with a parallel RC, the matching network has to obey
1/(2 pi RC) >= -integral (0 to inf) ln(1-|Gamma|),Where Gamma is the insertion gain. (I'm not 100% sure I'm quoting that righ t--it's in my book someplace.) There are more complicated versions for more complicated sources, iirc due to Darlington and other folks.
In any case, you can get a bunch more bandwidth by relaxing the return loss spec, but you use up your allowance fast if the mismatch isn't fairly unif orm.
T-coils separate the R and C, so they obey somewhat different rules and are generally better than LC peaking networks in the time domain.
Fun stuff, and sometimes very useful.
Cheers
Phil Hobbs
Or it isn't in thermodynamic equilibrium. A diode in the normal (not HL injection) region has a noise temperature of T_j/2. At zero bias, the reverse current equals the forward current, so you get the other half of the noise.
Cheers
Phil Hobbs
We tried a few and ended up with Acc Silicones SE3000 due to ease of potting, price and good enough conductivity. Here's a picture of a board where the silicone has been pried off by hand:
If I can get the current work in progress board drawn in time, I could do a test with SOT23 package, too.
In the test we actually had the TSSOP8 on top of a pertinax vero board with 0.100" holes and no copper to make its life even worse than in real world with copper GND planes and stuff.
-- mikko
Right it's not very useful, but I just wanted to see it with some conductor other than electrons.
George H.
Never heard of it.
George H.
Fancy! (Notwithstanding the ugliness that is PADS output. :-\ )
What's the annulus of pads in the center? Source from another delay line chain sort of thing, I would suppose. All the thin traces look like bias and sense.
12 stages is quite a lot for most transistors. There's tons of literature out there for every grad student's pet monolithic dist amp, and they don't usually push that many stages: too much loss. Fun way to get useful power gain at 80GHz though.Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
That's a screen capture, back in the 640x480 days or something.
I like PADS.
That thing produced 12 summed gaussian impulses spaced 250 ps apart. Each was programmable for amplitude. It was intended to be part of the beam modulator system for NIF. That board didn't work very well, but it looked cool.
This one did work:
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Is its neutron flux dangerous (in the typical scale of the device)?
Best regards, Piotr
Thanks Phil, and thanks everyone else who contributed suggested p/n. I figured it was past time for my own lifetime order. 25 of some is enough for me, or 100 to 200 of others. It took an hour to get my Digi-Key order ready, and by the time I finished, one item was no longer in stock! Realizing time was critical now, to beat other "grab-all-the-stock" buyers, I rapidly completed the Digi-Key order and thankfully found the other part still available at Mouser. Whoa!
--
Thanks,
- Win
All part of my nefarious plot to get the chipmakers to reconsider. ;)
It's sort of demoralizing designing stuff that nobody will be able to make, though. I have small hoards of some great parts such as the VA713 70-MHz O TA and some amazing Motorola dual-gate GaAs FETs, but I never seem to use t hem, even in one-offs. :(
Hopefully having a little instruments company and hoarding reels instead of cut tapes will help.
Cheers
Phil Hobbs
The last Distributed amplifier I worked with used 16 6146 tubes in a DC to 5 MHz video amp to modulate a TV transmitter. It was real fun matching a set of 16 tubes.
-- Never piss off an Engineer! They don't get mad. They don't get even. They go for over unity! ;-)
What did you use to do that? I have an old AVO valve (toob) tester somewhere; fantastic piece of kit it is, must have cost a fortune when first made. One day I'll get around to recommissioning it as I have a lot of toobs to evaluate for future sale. I've got the AVO transistor tester as well, too. That's another jaw-dropping piece of equipment. That old vintage stuff just screams quality.
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