lm339

[shubhra14]

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.

 

[ronsimpson]

Many circuits are like this: Problem is that it will not work.

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.

 

[alec_t]

Welcome to ETO!

can anyone please help me with the circuit diagram for lm339

Which particular circuit diagram?

 

[AnalogKid]

please help me with the circuit diagram

I completely agree - please help ***me*** by providing the circuit diagram.

ak

 

[shortbus=]

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?

 

[crutschow]

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.

 

[ronsimpson]

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)

Many people will put a LED and 2k resister in series for the output.

 

[shortbus=]

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.

 

[shubhra14]

thanks a lot everyone for your help. It really helped me.