The NAND gate is a universal gate that can be used to build every other type of logic gate. It can be built on a breadboard using only two transistors. The NAND gate is essential to making calculators and computers work. This is one of the simplest and most used digital logic gates. Most of the time the logic gates are incorporated into integrated circuits, computer memory, and computer processors.

nand gate with truth table and circuit diagram

The picture above shows a simple NAND gate circuit that is made on a breadboard using two 2N2222 NPN transistors, three 2K resistors, and a yellow LED. Power is supplied at 5 volts from a battery pack.

From the left, the first two resistors are inputs A and B. The input resistors connect to the base of the transistors.  If the resistor is in place the input is on as it connects to the positive 5-volt rail. If the resistor is removed the input is off.

This video shows how to build all types of logic gates. At 21:47 the NAND gate is discussed in detail. Understanding how all digital logic gates work is very important and I recommend watching the full video. This will make it so you can build calculators, computers, and even more advanced computational devices.

nand gate truth table

The truth table for a NAND gate shows when the output is on or off based on inputs A and B. In this case, the output is only off during the case when A and B are both on. Otherwise, the output will be on.

nand gate circuit diagram

The circuit diagram shows how to place the transistors, resistors, LED, and wires to make a NAND gate for demonstration purposes. In this case, when the output is on the LED will turn on. When building larger circuits the output will be sent further down the circuit.

NAND gates are often the primary logic gates used to build a computer. In the video above NAND gates are used to build data flip flops which are used to build the accumulator register, register B, and output register. NAND gates are also used to build full adders as part of the ALU.

Leave a Comment