Archive for June 2013
NAND Gate as OR Gate.
We
put NOT gates (obtained from NAND Gate as above) in both the inputs
of NAND gates; we get two input and
one output device resulting in the following truth table:
We have seen before that it is an OR truth table.
| A |
B |
Y |
| 0 |
0 |
0 |
| 0 |
1 |
1 |
| 1 |
0 |
1 |
| 1 |
1 |
1 |
NAND Gate as NOT Gate
If both inputs of a NAND Gate are combined, we get single output device
resulting in NOT Gate.
Truth table
A
|
Y
|
0
|
1
|
1
|
0
|
NOR
If we put an NOT Gate
at the output of OR Gate we obtain a
very useful combination called NOR
Gate. A NOR Gate has two or more
inputs but only one output. The NOR
function is the complement of OR
function.
It produces a value of true if and only if both operands are false. In other words, it produces a value of false if and only if at least one operand is true.
| A |
B |
Y |
| T |
T |
F |
| T |
F |
F |
| F |
T |
F |
| F |
F |
T |
If A and B are two
input then output is given by
Truth table for NOR Gate
INPUT
|
OUTPUT
|
|
A
|
B
|
Y = A
NAND B
|
1
|
1
|
0
|
1
|
0
|
0
|
0
|
1
|
0
|
0
|
0
|
1
|
SYMBOL
NAND and NOR Gate are called Universal Gate because we may obtain
all the possible Gates by using these individual Gates as basic building.
NAND and OR Gate may be used to
realize the basic logic functions OR,
AND, and NOT.
