Simple NAND gate.

Simple NAND Gate with LED. Shows the working of an NAND gate with a 5v source. I used 2 pulldown resistors to give the NAND gate the LOW input when the switches are open, otherwhise they would be floating and weird things can happen. Such as the NAND gate detecting a high input when floating, making the LED turn on even when the switches are open. The NAND gate works the same as a AND gate (see my other example). Instead of turning the OUTPUT of the NAND gate LOW when both inputs are HIGH. This is because there is a INVERTER (NOT gate) on the OUTPUT which "inverts" the OUTPUT of the AND gate. So it in short it is a reversed AND gate (which OUTPUT turns HIGH when both INPUTS are HIGH.) ----------------------------------------------------- Please bare in mind (altough not showing here) that besides the INPUT and OUTPUT pins the NAND 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 NAND gate would have 5 pins. 1 VDD (5volts) 2 VSS (Ground) 3 Input pin. 4 Input pin 5 Output pin. The NAND gates come in a variety of "packages" (ic's). For example a NAND Gate with 3 or 4 INPUTS. There are also IC'S with 2 or more NAND Gates on 1 IC.

published 11 years ago