[SOLVED] Question regarding LM339 comparator.

Good day Guys...i have lm339 comparator. Let say i have Vcc (+VSupply) and ground (-VSupply). So my question is...if the inverting input is having higher voltage than non-inverting input...is it the ouput will be 0 or grounded? Which means any potential/voltage connected to the output will be grounded also? Thanks a lot.

I have used these devices many times in the past and when I saw your post I thought "Ahrrr, it's not a dual supply part!"WRONG! You are correct, it is a single supply OR dual supply.

If you examine the output circuitry it is an open collector to the GND or -V supply, so if you use a -V supply the output will be switched to that also.

There used to be a comparator if my memory serves that had a seperate ground pin for the output so it could effectively work bipolar but provide a unipolar output. I'll have a think........

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Found it! It was the similar numbered part LM319.

These came in dual packages and they had +V, -V which could be bipolar or unipolar (even+5V only) and also Gnd1 and GND2, one for each output.
The outputs could be "wired OR" which made them a useful window comparator. I couldn't find a good dual supply powered circuit with say TTL pullup for the output, but I'm sure that's how they can be used if required.

So in short...am correct to say that the output will be grounded if -V is higher than +V ???
Thanks for the reply and sharing your experience.

So in short...am correct to say that the output will be grounded if -V is higher than +V ???
Thanks for the reply and sharing your experience.

Click to expand...

Hi RHeTTRoNiCS
If your mean by -v is inverting input and if minus supply rail is tied into the ground then yes that's true .
Best Wishes
Goldsmith

Let say i have Vcc (+VSupply) and ground (-VSupply).

Click to expand...

Yes the output will go to whatever voltage the ground pin which is also the -V supply pin is at.

The typical schematics are confusing as the -V supply pin can also function at 0volts and is often shown this way with a ground symbol.
As said the output will pull down to the potential on this pin which as Goldsmith states will be ground if the -V supply is at Ground potential.

Lots of words for a simple answer!!!!