Hello,

Please refer to the attached images. I got the LM339's LTSpice model from https://github.com/evenator/LTSpice-Libraries/blob/master/sub/LM339.sub
I connected the circuit like that shown on the image and expected the output voltage, Vout, to be 1, a digital signal. However, the output is 17.2mV. I would like to know if this is my mistake or something wrong with the model?

 

Did you account for the fact that the 339 is open collector output?

 

LM339 is an open-collector comparitor, you need a pullup resistor to see the output signal

 

Don't know how that slipped passed me. Thanks!

 

I connected the circuit like that shown on the image and expected the output voltage, Vout, to be 1, a digital signal.

Why are you using a simulator for such a simple circuit? That's kind of like using a calculator to add 2 + 3.

 

For single supply situation, If neg is > pos output = 0, if neg < pos it goes high. For a simple comparator when both are equal it can go either way with actual component, hysteresis helps that issue and also mitigates oscillation.

The mV you see is min output voltage at the lower rail.

 

Why are you using a simulator for such a simple circuit?

Because it showed him that the circuit doesn't work, so he needs to change the design.
It helps keep one from building an incorrect circuit.