Understanding Gates – NOR Gate

The NOR Gate inverts the output of the OR Gate. Let’s see how it’s done in this episode.

Your key takeaways are:

• NOR has an inverter after the OR Gate
• Opposite output state as the OR Gate
• If both input states are false, then the NOR output computes to true
• Else it’s false

Study Notes

What makes the output of an OR Gate true? Since it runs in parallel, if one or the other state is true, then the output is true.

So, for a NOR Gate, if both states are false, then do something.

Let’s compare the two:

OR Gate

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

Here is the condensed OR gate truth table:

OR	0	1
0	0	1
1	1	1

NOR Gate

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

Here is the condensed NOR gate truth table:

OR	0	1
0	1	0
1	0	0

The NOR Gate is the opposite state of the OR Gate. If you know how an OR Gate works, then you know how the NOR gate works!

What gives us the opposite state of an OR Gate? Hopefully, you remember it from the NAND Gate: an inverter!