Simple NOR Gate.

Simple NOR Gate with LED. Shows the working of an NOR gate with a 5v source. I used 2 pulldown resistors to give the NOR gate the LOW input when the switches are open, otherwhise they would be floating and weird things can happen. Such as the NOR gate detecting a high input when floating, making the LED turn on even when the switches are open. The NOR gate OUTPUT turns HIGH "only" when both of the INPUTS are LOW. When "at least" 1 INPUT is HIGH the OUTPUT turns LOW. It is a OR gate with a NOT gate tied together. So it inverses the OUTPUT of the OR gate. ----------------------------------------------------- Please bare in mind (altough not showing here) that besides the INPUT and OUTPUT pins the NOR gate also has VDD (5Volt) and VSS (Ground) pins which need to be connected to 5 Volts and GROUND. This makes it possible for the LED to turn ON even when the switches are open. This NOR gate would have 5 pins. 1 VDD (5volts) 2 VSS (Ground) 3 Input pin. 4 Input pin 5 Output pin. The NOR gates come in a variety of "packages" (ic's). For example a NOR Gate with 3 or 4 INPUTS. There are also IC'S with 2 or more NOR Gates on 1 IC.

published 11 years ago