When you say pull up resistor, do you mean a resistor in series with the load(as shown in the drawing below) or do you mean in parallel with the load i.e. a resistor between the output(pin 7) and 0V.I connected it up as shown in the drawing below and the LED didn't light up when the input voltages where compared.
I even had the +ve input at 4V and the -ve input at 1V and still it didn't light up the led.
Do you think It can operate on only a single supply?
If it can then maybe the IC is fried but I only just bought it,so guess not.