LM339 Question
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Hello all,
Dose any one know if I can use A LM324 inplace of a LM339 for a
project? The sheat that I got says to use a LM339, well I got a LM324
that I had laying around.
please help
TC
Dose any one know if I can use A LM324 inplace of a LM339 for a
project? The sheat that I got says to use a LM339, well I got a LM324
that I had laying around.
please help
TC
Comments
>Hello all,
>
>Dose any one know if I can use A LM324 inplace of a LM339 for a
>project? The sheat that I got says to use a LM339, well I got a LM324
>that I had laying around.
>
>please help
>TC
The short answer to your question is YES because you are using an
Op-Amp in-place of a Comparator. If you were using a Comparator
in-place of an Op-Amp, I would be more hesitant to say YES.
...your circuit however might require a diode on the output on
each Comparator...
Old Output >
|<----> New Output
...The diode allows the remainder of the circuit to "think" that
it has the "open-collector" outputs on the OP-Amp (LM324) that
would typically be on a Comparator. (See below) ...although it
is possible that the circuit doesn't care either way, you may not
even need the diodes.
Your question is more of an application dependent question...
The most substantial difference between a Comparator (LM339) and
an Op-Amp (LM324) is that the Comparator is Open Collector, meaning
that it is never driven HIGH.
In most circuits where a Comparator is used, it might be ok to
substitute an Op-Amp.
On the other hand, in circuits where an Op-Amp is used, it is
unlikely that a Comparator could be used as easily. But again, this
mainly depends on the application.
See: http://www.national.com/pf/LM/ for a list of datasheets....
...under the LM339, take a look at page 15 and compare that
schematic to the LM741 page 4, and see how much they differ.
The Op-Amp is driven both HIGH and LOW, while the Comparator
is only driven LOW.
Beau Schwabe IC Mask Designer
National Semiconductor Wired Communications Division
500 Pinnacle Court, Suite 525 Mail Stop GA1 Norcross, GA 30071
>Hello all,
>
>Dose any one know if I can use A LM324 inplace of a LM339 for a
>project? The sheat that I got says to use a LM339, well I got a LM324
>that I had laying around.
May work, may not.
1st - they have different pin outs. If you have a board laid out for the
339, the 324 will definitely not work.
2nd - the 339 has open collector outputs.
3rd - the 339 switches it's output (slews) at least 100 times faster than
the 324.
If none of these differences affect you, the 324 will work just fine.
dwayne
Dwayne Reid <dwayner@p...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax
Celebrating 17 years of Engineering Innovation (1984 - 2001)
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