XNOR Gate Definition
XNOR Gate is a digital logic gate used in various digital
electronic circuits to perform logical functions. It is also called X-NOR Gate or Ex-NOR Gate or Exclusive-NOR
Gate.
The XNOR gate is a two-input and one digital output logic
gate.
The XNOR gate is basically a combination of an XOR gate (Ex-OR gate) and a NOT gate.
The XNOR gate gives a HIGH (Logic 1) output only when both of
its inputs are the same, i.e. 0 and 0 or 1 and 1. The output of the XNOR gate
is LOW (Logic 0), when both of its inputs are different, i.e. one input is a 0 and
the other is a 1.
The XNOR gate is also known as a coincidence gate, as it gives a HIGH (Logic 0) output only when both
of its inputs coincide, i.e. same.
In digital electronics, the XNOR gate can be used as an equality detector, as it gives a HIGH output
when its inputs are equal.
Note:
It is important to note that three or more variable XNOR
gate does not exist. If we require three or more variables to be XNORed,
then multiple XNOR gates are connected together to achieve the desired number
of input variables.
XNOR Gate Symbol
The symbol of the XNOR gate is depicted in the following
figure.
It has two inputs, say A and B, and one output represented by Y.
XNOR Gate Truth Table
The truth table of a two-input XNOR gate is shown below:
|
Inputs |
Output |
|
|
A |
B |
Y |
|
0 |
0 |
1 |
|
0 |
1 |
0 |
|
1 |
0 |
0 |
|
1 |
1 |
1 |
XNOR Gate Boolean Expression
If A and B are the input variables and Y is the output variable
of the XNOR gate, then the Boolean expression for the output of the XNOR gate
is given by,
This Boolean expression is read as Y is equal to A XNOR B.
XNOR Gate Switching Circuit
The switching circuit diagram of an XNOR gate is shown in
the following figure.
It consists of a battery, a lamp, and two switches namely A and B.
In this switching circuit, when both switches are connected
to logic 1, the circuit will be completed and the lamp will glow. When both switches are connected to logic 1, then the circuit will be also completed
in this case, turning the lamp ON.
But, when switch A is connected to logic 1 and switch B is connected to logic 0 or when switch A is connected to logic 0 and switch B is connected to logic 1. In these two cases, the
circuit is not complete, and no current flows in the loop. Thus, the lamp
remains OFF.
This is how the above-shown switching circuit implements the
XNOR gate logic.
XNOR Gate IC
There is an integrated circuit namely, “74266 Quad 2-Input
Ex-NOR Gate” available in the market. The schematic diagram of the 74266 XNOR
gate IC is shown in the following figure.
This 14-pin IC has four 2-input XNOR gates within it.
Hence, this is all about the XNOR logic gate in digital
electronics.
Other Useful Resources
You can get more knowledge about XNOR gate from the following useful resources.
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