What does a comparator do ?

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

jbelectric777 said:

I just want to know ... Jim

Click to expand...

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

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.

jbelectric777 said:

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

Click to expand...

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...

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

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

https://www.electro-tech-online.com/custompdfs/2007/04/LM339.pdf

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

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: https://www.datasheetarchive.com/