Hi all, I have a comparator LM339M, what is its main purpose ? It has 4 inputs and 4 outputs as well as a Vcc and ground connection. When do the outputs go high ? Can you explain the basics. I do'nt have a specific purpose intended for it, I just want to know when outputs 1-4 go high or low and when and why..... Thanks in advance.... Jim

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"Yesterday is History, Tomorrow's a Mystery"

 

Check out this site for all you ever need to know: home.cogeco.ca/~rpaisley4/Comparators.html

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Creationists have a world of evidence

 

Here is a great site that will help you to understand most electronic devices, and it's FREE.

http://www.datasheetcatalog.com/

The information comes straight from the manufacturers, its faster than posting a question, and you can depend on the acuracy.

 

LM339 sounds like an analog comparator... These have two inputs and one output...

One of the input is called the non-inverting input (+) while the other is an inverting input (-)

When the voltage at the + terminal exceeds that at the - terminal, the output is high.

When the voltage at the - terninal exceeds that ath the + terminal, the out put is low.

Ex:
+ = 2.5v
- = 6v
Output =Low...

if
+ =5
- =-6
Output=High...

There are also some digital comparators...

Where two digital words are compared and the output is either 1 or 0...

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Bharath Bhushan Lohray.
M.Sc. Electronics.

 

I think 339 needs a pull up resistor to output positive.

Here's the data sheet ,you should get used to reading them.

http://downloads.solarbotics.com/PDF/LM339.pdf

You can usually google for a device number and find a data sheet.

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Reality

 

LM339 is a current sinking comparator, so the outputs are either tied to ground, for a logic 1, or high resistance, for a logic 0.

 

It is basically a saturating op-amp. A little more complicated but that is pretty much what is happening.

I always use this site when I come across a part I do not know: http://www.datasheetarchive.com/