Comparator.Unable to get proper output

[natrajgn]

Hi All,

I am trying to rig up a comparator ciruit using LM339.I have supplied 12 to pin 3(Vcc) and pin 12(Vdd) has been grounded.Two resistors each 10k has been used as voltage devider and has been supplied to pin 5(non-inverting).

Now pin 5 has a voltage of about 6v. I tried supplying 0v and 12v to pin 4(inverting).In either of the case i got the same voltage i.e aroung .2v in the output pin 2 with respect to the ground.The voltage is not changing when the input voltage at pin4 crosses reference voltge

I am trying build the following project.Instead of TL071, i am using LM339.
**broken link removed**

Could some one help me on this.

Nataraj

 

[aProgrammer]

LM339 has a open collector output and need a resistor from vcc to output.

example : **broken link removed**

 

[natrajgn]

Thanks for the repply.Well i have done that.

Looks like i was not providing negative supply voltage.
Can some body confirm, LM 339 needs negative supply voltage to operate properly.