Windo comparator using LM311 to compare between 3.3v to -24vdc

Thread Starter


Joined Apr 6, 2012
Dear Sirs,

Using NI Multisim version 13.0, windo comparators works fine when comparing voltages between 9 to 24Vdc.
However it fails when comparing 3.3 to -24vdc.
Will the comparator, LM311 able to compare the 3.3 to -24vdc?

Any help in this would be very much appreciated.

Thread Starter


Joined Apr 6, 2012
Hi Thanks for the help.

1. I have given the right voltage supply (in MultiSim) still no luck.

2. Supply voltage is +/- 18 volts. The upper and lower limys are 3.3v and -24volts. Sensing voltage is -10v.

I will post the drawing tonight (Sorry at work now)



Joined Sep 16, 2012
It looks like your supply is negative and you've given it a '-18V'... that's a double negative, making a positive. Change the polarity of your negative voltage or remove the '-' from the voltage level... not both. Then your sim should work.


Joined Mar 14, 2008
Note that ±18V is the absolute maximum supply voltage allowed for the LM311. You should keep it no greater than ±15V for reliability. Also the worst-case input voltage range is 13V to -14.5V. If you need to detect input voltages higher then that, you can use resistive voltage dividers (bridge circuit) on the inputs.