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.

AND gate truth table and symbol

The logic or Boolean expression for an AND gate is A.B = Q 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

AND gate symbol
Input AInput BOutput Q

3-input AND Gate Truth Table

3-input AND gate symbol
Input AInput BInput COutput Q

IC Alternatives with AND Gates

Pinout for the 4081 IC

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.

Simple circuit to test an AND gate

More Logic Gates Tutorials

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