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lm339

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shubhra14

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hey can anyone please help me with the circuit diagram for lm339 for voltage comparison with proper value of resistor. i have tried all online circuits but it is giving very low output as for 5v input its giving only 300-400 mv . and also led is not glowing.
can anyone help please.
thank a lot in advance.
 
Many circuits are like this: Problem is that it will not work.
1554226085793.png

Note on this one there is a pull up resistor on the output. The LM339 only pulls down. The resistor is needed to make the output go up.
1554226144728.png
 
Can I join in? What is the best resistance level to use on the inputs? Or would that be impedance instead of resistance? What value is commonly used?
 
What is the best resistance level to use on the inputs?
The maximum resistance is generally limited by the offset you can tolerate due to the input bias currents.
 
best resistance
I chose 10k & 10k on the (-) input. But 2.2k through 2.2 meg will be fine.
On the output I chose 10K to be simple but 1k through 100k is OK.
I added a 10K pot to the (+) input. But almost any pot will work. (2k through 2 meg)
1554246497233.png

Many people will put a LED and 2k resister in series for the output.
 
Thanks for the answers, the reason I asked was you see all kinds of values used in web posted circuits. And reading the data sheet doesn't give any help or I don't know the correct term to look for in the DS.
 
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