Logic Gates
Controlling electricity gives us the ability to make yes and no decisions or
true
and false
. By combining two signals, we can give a single true
or false
answer, depending on the logic
. The flow of electricity is controlled using gates
(no, not named after Bill Gates - like a gate).
Standard Logic Gate Symbols
NOT
AND
NAND
OR
NOR
XOR
XNOR
All Truth Tables
The simplest gate, this item
inverts
or reverses the signal. 
Input (A) | Output (Q) |
0 | 1 |
1 | 0 |
Only outputs true if both inputs are true.

A | B | Output (Q) |
0 | 0 | 0 |
0 | 1 | 0 |
1 | 0 | 0 |
1 | 1 | 1 |
Any gate with a dot is an
inverted
gate.
This is the NOT AND gate:

A | B | Output (Q) |
0 | 0 | 1 |
0 | 1 | 1 |
1 | 0 | 1 |
1 | 1 | 0 |
One or the other or both!

A | B | Output (Q) |
0 | 0 | 0 |
0 | 1 | 1 |
1 | 0 | 1 |
1 | 1 | 1 |
Very simply NOT OR.

A | B | Output (Q) |
0 | 0 | 1 |
0 | 1 | 0 |
1 | 0 | 0 |
1 | 1 | 0 |
Exclusive OR meaning only one is true, not both.

A | B | Output (Q) |
0 | 0 | 0 |
0 | 1 | 1 |
1 | 0 | 1 |
1 | 1 | 0 |
Exclusively NOT OR. If both inputs are the same, output true.

A | B | Output (Q) |
0 | 0 | 1 |
0 | 1 | 0 |
1 | 0 | 0 |
1 | 1 | 1 |
The two "universal" gates are
NOR
and NAND
- it is said that you can create all the other logic gates with a combination of just these two.There are tons of videos available about logic gates. If I had to pick a favourite, my current is this one, although she talks incredibly fast and you might need to slow it down or rewind.
Last modified 4yr ago