[SOLVED] Question regarding LM339 comparator.

[RHeTTRoNiCS]

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.

 

[pinout]

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.

 

[RHeTTRoNiCS]

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.

 

[goldsmith]

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.

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

 

[pinout]

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

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!!!!