RHRRC said:
Bulk buying stock for the next 3 years is certainly an option
that has been considered.
Somehow I dont like the idea of knowingly using a part which
is no longer available. Somebody's law says that many more,
or zero, will be required and that a bulk purchase will all
be right at the bottom of the spec (devices with a particularly
low gain cannot be used).
Win - I am sure you must have come across such an animal as
is needed here.
I live in hope.
What does this part do, what's it used in? How much current
and voltage are you switching, what's the flyback voltage?
It's interesting that the BUV48 is mentioned as a high-voltage
power transistor in ST's old an656 app-note on reading power-
transistor datasheets. Hmm, I wonder if that had anything to
do with its being chosen?
Let's talk about power-transistor packages. As you know,
I'm sure, the TO-220 and its cousins were designed to be
able to replace TO-3 metal-can packages, in that the hole
in the tab and the base and emitter leads are located to
drop right into an unmodified PCB. Now, as for whether a
TO-220 or some other larger package is used, the parameter
to consider is the part's thermal resistance. And, as it
happens, this is determined primarily by the size of the
die inside the package, and not by other aspects of the
package, except of course, an insulating layer, like you
have in your BUV48AFI.
BTW, the BUV48 has a rather large die, no doubt associated
with its capability to switch 15 amps, although one has to
say, not very well! That's because at 15A it has a high
5V saturation voltage, despite being driven by 3A of base
current, for a low saturated-drive beta of only 5. Anyway,
I'd say the large die puts this part in an small group.
(This part's low gain, BTW, comes from its high 1000-volt
Vces rating. Do you need that capability?)
I doubt you're using the BUV48 at such high currents, but
as stated, besides saturation voltage at a given base drive,
an important parameter is the part's thermal resistance.
One transistor you could consider is ON Semi's MJF18008,
which comes in a "fullpack" insulated package.
Vce(sat)
Vces at Ic RthJC
BUV48AFI 1kV 1.5V 8A 2.2C/W
MJF18008 1kV 0.7 4.5 2.78
This part does have a smaller die, hence the lower Ic value
used for the saturation spec, and the higher Rth specs, but
it's not a wimp; it's saturation-voltage plot shows about
Vce 1.5V at 8A, like the BUV48. Anyway, any replacement
decision would depend on how you're using the transistor.
There are larger parts, of course, but not many made with
the fully-insulated feature. Fairchild has an insulated
high-current part, but with a slightly lower 800V Vcbo.
Vce(sat)
Vces at Ic RthJC
BUV48AFI 1kV 1.5V 8A 2.2C/W
FJPF13009 800V 1.5V 8A 2.4C/W
That one looks pretty similar to yours, and shows that
the TO-3P, etc., vs. TO-220 package isn't responsible for
the high-current performance.
