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RE: LEDs



Subject:   RE: LEDs
  Date:   Wed, 7 May 97 07:48:03 UT
  From:   "William Noble" <William_B_Noble-at-msn-dot-com>
    To:   "Tesla List" <tesla-at-pupman-dot-com>, tesla-at-poodle.pupman-dot-com


No attempt to format line length - one <CR> per paragraph - here's one
now
I happened to have the 1979/80 litronix catalog handy, so I looked in it
to 
see what it had to say about LED forward voltage drop.  Since this is an
LED 
company, they list many pages of various LEDs.  For RED LEDs, they show 
forward voltage drops of :
Red     1.6 typical, 2.0 max,  and 2.4 volts typical, 3.0 max.
Orange  1.7 typ, 2 max
Yellow  2.4 to 2.7 typ, 3. To 3.5 max
Green   2.4 to 2.7 typ, 3.o max
IR      no forward voltage drop listed (I wonder why???)
Another catalog lists IR diodes in retroflective sensors as having a 1.8
volt 
forward drop.  

Sorry I don't have any reasonably recent catalogs handy but it looks
like my 
.7 volt statement was wrong, the range seems to be 1.6 to 3 volts
depending on 
some unknown factors (like substrate material and doping).  I seem to
recall 
that blue has a higher drop, but blue LEDs are newer than my catalog
Giant snip