Sadegh.j said:You can choose your own Vdd, as simple as that.
This means that without a pull up resistor, a logic 1 might represent 5V, with it, it might represent 20V. Watch out, you might damage the IC.
diegobb said:If the current in the resistor is zero, the voltage drop is zero too, so the output goes to +Vcc (In most of the cases 5V). I hope this will help you. I will in the same problem a lot of time ago. (Remember that the oputput is floating, so it takes the voltage you put externally).
I hope this will help. Bye and good luck.
A.Anand Srinivasan said:the current through the resistor will become zero only when the output voltage of the IC and that of Vdd are equal... this is achieved only based on the output swing of the IC.....