[SOLVED] OP AMP LM2903 as a Comparator

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kushipoorvi

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Hi,
I'm using LM2903 IC as a Comparator. Single Supply voltage 24V.
non inverting I/P i.e as ref 12V and inverting I/P 24V. i want to get output as 3.3V. my question is is it ok to use I/P voltage same as Supply voltage and wat i hav to do for getting output as 3.3V .

thanks and regards

poorvi
 

Hi,

LM2903 is no opamp, it is a comparator. So you use it the right way.

is is it ok to use I/P voltage same as Supply voltage
Click to expand...
You find the answer in the datasheet "input voltage". You see it is the same as the supply voltage. But there is no tolerance for higher voltage. So i recommend not to go to absolute maximum limit.

But you must not connect both inputs to supply rail, because "common mode input voltage range" = V+ -1.5V. (but you have 12V ref at +IN, so everything is OK)


wat i hav to do for getting output as 3.3V .
Click to expand...
LM2903 is a comparator with open dran output, therefore: Just connect a pullup resistor (maybe 10k) to 3V3 to the output.


Klaus
 
hi,
The Common voltage allowed is less than the Vsupply, look at this image from the d/s.
Is it possible you could use a resistive divider to reduce the 24Vinp to say 12v.??

As the output is open collector, use a 1K resistor from the output to 3.3V to get a 3.3V output swing.

E
 

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