Understanding Gates – NAND Gate

The NAND Gate is a combination of the NOT and AND gates. First, it processes the AND portion. Then it inverts it.

Your key takeaways from this episode are:

• NAND has an inverter after the AND Gate
• Opposite output state as the AND Gate
• If both input states are true, then the NAND output computes to false
• Else it’s true

Study Notes

An NAND Gate is a combination of the following gates:

• one AND Gate
• one NOT Gate

The NAND Gate is simply an AND Gate with an inverter on the output. Therefore, whatever the output from the AND Gate is, it is inverted or flipped to the opposite state.

Comparing AND Gates and NAND Gates

AND Gate

Switch 1	Switch 2	Light bulb
1	1	1
0	1	0
1	0	0
0	0	0

Here is the condensed AND gate truth table:

AND	0	1
0	0	0
1	0	1

NAND Gate

Switch 1	Switch 2	Light bulb
1	1	0
0	1	1
1	0	1
0	0	1

Here is the condensed NAND gate truth table:

NAND	0	1
0	1	1
1	1	0

For the AND Gate, both switches must be on for the output to be on (true.) However, for the NAND Gate, if both switches are on, it is off (false.) Otherwise, the NAND Gate will output on (true.)