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Am I being International Rectifiered again?

T

Tim Williams

Jan 1, 1970
0
http://www.fairchildsemi.com/ds/FG/FGA30N120FTD.pdf

Maximum collector current 60A at 25C. I don't see any condition, taking a reasonable guess at Vce(sat) at max Tj, where this could possibly dissipate anywhere near the power rating of 339W (also at Tc = 25C). In fact, the typical output characteristics show it should be closer to Vcesat = 3V, Ic = 120A, Vg = 15V. So why pick 60A?

More BS? What's the real rating? Buy from someone else? Ha, no one else even has honest ratings...

Tim
 
J

Joerg

Jan 1, 1970
0
John said:
I'd go for the headline: 30 amps. That's achievable, without a lot of
switching losses or water-cooled diamond heat sinks. The 339 watts is
absurd.



Looks like everybody has to keep up with IR. They should add to "Abs
max ratings"

MAXIMUM LIES 12 typ

It can get worse. I saw an audio amp in a blister pack, IIRC at a
Walmart. Said 1000 watts PMPO on the label and the power supply was a
wall wart ...
 
T

Tim Williams

Jan 1, 1970
0
Jan Panteltje said:
That leaves a heatsink of .42 °C / W.
Fan? processor cooler? Heat pipes?

T_HS = 40C is pretty easy to arrange, I intend on water cooling anything this powerful.

Tim
 
http://www.fairchildsemi.com/ds/FG/FGA30N120FTD.pdf

Maximum collector current 60A at 25C. I don't see any condition, taking a reasonable guess at Vce(sat) at max Tj, where this could possibly dissipate anywhere near the power rating of 339W (also at Tc = 25C). In fact, the typical output characteristics show it should be closer to Vcesat = 3V, Ic = 120A, Vg = 15V. So why pick 60A?

More BS? What's the real rating? Buy from someone else? Ha, no one else even has honest ratings...

Tim

Yes.

This is a kind of cyclical thing in electronics. Specsmanship gets
quoting ever more unreasonable values driven by things like "infinite
heat sinks". Eventually there are too few old dogs to keep the punks
from believing the spurious ratings. Failures and then lawsuits
follow like Nemisis following Hubris. Then the specs get more
realistic again for a while, then sales critters insist on bending
them again. There is a deficit of memory in the beauracracies that
causes this oscillation.
 
It can get worse. I saw an audio amp in a blister pack, IIRC at a
Walmart. Said 1000 watts PMPO on the label and the power supply was a
wall wart ...

I remeber outrageous PMPO ratings from well over 40 years ago.
Something not much bigger than a small 3-1/2 external drive case,
rated at 100 W per channel stereo including power supplies. Middle to
late 1960s. They're baack.
 
T

Tim Williams

Jan 1, 1970
0
This is a kind of cyclical thing in electronics. Specsmanship gets
quoting ever more unreasonable values driven by things like "infinite
heat sinks". Eventually there are too few old dogs to keep the punks
from believing the spurious ratings. Failures and then lawsuits
follow like Nemisis following Hubris. Then the specs get more
realistic again for a while, then sales critters insist on bending
them again. There is a deficit of memory in the beauracracies that
causes this oscillation.

Hmm, I wonder if that oscillation is in phase with the "component shortage" oscillation.

Tim
 
T

Tim Williams

Jan 1, 1970
0
John Larkin said:
We are now seriously into yet another silicon fab shortage. Lead times
are skyrocketing into the triple-digits-of-weeks, people are
multiple-ordering, brokers and counterfeiters are cashing in, the
usual cycle.

Fortunately, there are still large stockpiles of common parts, like 2N3904s and LM393s. That's fine for me, if not for people who need fancy things.

I'm more concerned about finding capacitors suitable for induction heater use. I found two series, by Epcos, which look good. One has shown the same lead time for years, I haven't bought any since the first tank cap;
http://webpages.charter.net/dawill/tmoranwms/Elec_CapBank.html
the other is gone entirely (in fact, I just bought Digikey's remaining stock). And these are just regular MKPs. The other cheap caps, like Illinois Capacitor or BC Components' MKP lines, have way too much ESR.

Tim
 
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