AND Gate – Logic Gates Tutorial

An AND gate is a logic gate where the output goes HIGH (or “1”) only if all its inputs are HIGH. So if the inputs A AND B are HIGH, the output Q will also be HIGH.

The logic or Boolean expression for an AND gate is which means that:

If A and B are true, then Q is true

Truth Table

AND gates can have more than two inputs. But no matter how many inputs it has, it will only give out a HIGH or logic “1” if all its inputs are HIGH. As soon as one of the inputs goes LOW, the output goes LOW too.

2-input AND Gate Truth Table

Input A	Input B	Output Q
0	0	0
0	1	0
1	0	0
1	1	1

3-input AND Gate Truth Table

Input A	Input B	Input C	Output Q
0	0	0	0
0	0	1	0
0	1	0	0
0	1	1	0
1	0	0	0
1	0	1	0
1	1	0	0
1	1	1	1

IC Alternatives with AND Gates

If you want to experiment and build circuits with AND gates, you’ll find them in both the 4000 IC series and the 7400 IC series:

• 4081: Four 2-input AND gates
• 4073: Three 3-input AND gates
• 74HC08: Four 2-input AND gates (HC is the family, can also be LS/HCT/…)
• 74HC09: Four 2-input AND gates (HC is the family, can also be LS/HCT/…)
• 74HC11: Three 3-input AND gates (HC is the family, can also be LS/HCT/…)

These should all be available as hobbyist-friendly through-hole chips. Just make sure you buy the DIP package version.

Example Circuit: Testing the AND gate

Below is a circuit that you can build to demonstrate how an AND gate works.

Normally, both inputs to the AND gate are LOW because of the pull-down resistors. When you push any of the push buttons, you’ll make the input pin HIGH.

The Light-Emitting Diode (LED) on the output shows the result. A lit LED represents a HIGH output. An unlit LED represents a LOW output. As you’ll see, the LED will only turn on if you push both buttons at the same time.

More Logic Gates Tutorials