[Amps] 1N5408 vs 1N5553

[Jim Garland]

> >From a quick search it appears that the 1N5553 reverse current is 1ua,
and
> the 1N5408 is 5ua, both at 25*C. Leakage goes up with temperature.
> 
> Carl
> KM1H
> 

I was surprised to learn that the 1N5408 is made by at least 29 different
manufacturers
(http://www.datasheetcatalog.com/datasheets_pdf/1/N/5/4/1N5408.shtml) , and
specs vary slightly among the group. General Semiconductor gives the reverse
leakage (25 degrees C) as 5 uA, while On Semiconductor specifies it as 10
uA.  On Semiconductor gives the 150C reverse current as 100uA, whereas
Semtech gives the 105C (not 150C) leakage current as 500 uA. Everbody agrees
the 1N5408 is rated at 3ADC (with leads of about 1/2 inch).

The 1N5553 also shows some variation among different manufacturers, though
most agree that the reverse leakage current at PIV is 1 uA at 25C, rising to
20uA at 100C.  All manufacturers specify the switching speed of the 1N5553
at 2 usec, and nobody specs the switching speed of the 1n5408. Don't know
why. The 1N5553 is rated at 5ADC with 3/8 in. leads, or 3A DC, with shorter
leads.

You can buy one 1N5408 from Mouser for $0.15 (Taiwan Semiconductors). Mouser
stocks tens of thousands of them. Mouser says the 1N5553 is now obsolete and
no longer stocks them. Newark still sells them, however, and prices have
plummeted to about $1/ea in quantities of 1000. A few months ago, when they
were still in production and "military approved," they were selling for
about $16/each.  Maybe Uncle Sam finally wised up!  (FYI, I bought fifty
from a local surplus dealer for $5. Nice little diodes.)

73,
Jim W8ZR