Building logic circuits

Single gates are building blocks. Connect them together and you can create circuits that make decisions and process information.

The first few examples should feel familiar...

AND → NOT = NAND

Feed the output of an AND gate into a NOT gate. The result is only 0 when both inputs are 1.

A
B
0
AND
1
Q
A B AND Q (NAND)
0001
0101
1001
1110


OR → NOT = NOR

An OR gate followed by a NOT gate. The output is 1 only when both inputs are 0.

A
B
0
OR
1
Q
A B OR Q (NOR)
0001
0110
1010
1110


AND + OR (three inputs)

A and B feed an AND gate. That result, plus a third input C, feed an OR gate.

Logic formula:

Q = (A AND B) OR C
A
B
C
0
A·B
0
Q


Advanced alarm circuit

The alarm activates if the system is armed AND the door opens, or if the panic button is pressed.

Formula:

Q = (Door AND Armed) OR Panic
D
A
P
0
ALARM


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