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Implementation of XOR Gate from NAND Gate

Last Updated : 03 Apr, 2025
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Logic Gates are the building blocks of digital circuits, taking binary values as input and returning a binary value as output after performing a logical operation. There are several kinds of gates available in Digital Electronics like basic gates, and universal gates. Implementation of the XOR gate from the NAND gate is possible because the NAND gate is a Universal gate i.e., it can implement all other gates. The NAND gate gives the output 0 if all the inputs are 1 else it gives 1 for all other cases. XOR gate is a logic gate that gives output 1 when number of 1s in input are odd else it gives 0. In this article, we will explore the XOR gate, and NAND gate and implement the XOR gate from the NAND gate.

What is an XOR Gate?

In digital electronics, the XOR (Exclusive-OR) Gate is a combination of all three fundamental or basic gates (NOT, AND and OR gates). It receives two or more than two input signals but produces only one output signal. It results in a low (0) if the input bit pattern contains an even number of high(1) signals. The output is high (1) for an odd number of high (1) signals in the input bit pattern.

The XOR gate's behavior can be summarized as follows

Returns 1, if the number of logical high input is odd.

Returns 0. if number of logical high input is even.

The Boolean Expression of two input XOR Gate is as follows

Say we have two inputs, A and B and the output is called X, then the expression is:

X = A⊕B = A’B + AB’

XOR Gate
2 Input XOR Gate

Logic Diagram of Three Input XOR Gate

The logic circuit diagram of the XOR gate is shown in the following figure. It has three input line denoted by the letter A, B, C and one output line denoted by the letter X, where X=A⊕B⊕C.

3 Input XOR Gate
3 Input XOR Gate

Here, we can see that when the number of 1s in the input is odd, the output is also 1.

Say we have N inputs, A0, A1, ...., AN and the output is called X, then the expression is:

X=A0⊕A1⊕.....⊕AN.

What is a NAND Gate?

NAND Gate is a combination of AND and NOT Gate. In this gate, a NOT Gate is applied at the output of an AND Gate. It receives two or more than two input signals but results in only one output signal which is complement of product of all the input signals. This is the reason that a NAND Gate is also referred as complemented AND Gate or Inverted AND Gate.

The NAND gate's behavior can be summarized as follows

Returns 1, if all the inputs are 0 or alternative (meaning one is 0, and the other is 1 or vice versa).

Returns 0, if all inputs are 1.

The Boolean expression of two input NAND Gate is as follows

Say we have two inputs, A and B and the output is called X, then the expression is:

X = (A . B)’

2 Input NAND Gate
2 Input NAND Gate

Logic Diagram of Three Input NAND Gate

The logic circuit diagram of the NAND gate is shown in the following figure. It has three input lines denoted by the letter A, B and C and one output line denoted by the letter X, where

X= (A.B.C)'

3 Input NAND Gate
3 Input NAND gate

Implementation of XOR Gate from NAND Gate

Expression of XOR gate: A'.B + A.B'

To convert the expression into NAND form perform the following:

Apply double complement: [(A'.B + A.B')']'

Operate internal complement: [ (A'.B)' . (A.B')' ]'

Now, expression is obtained in NAND form.

Pass Input A through the first NAND Gate to get A', now pass this A' and B through the second NAND Gate to get (A'.B)'. Similarly, pass Input B through the third NAND Gate to get B', now pass this B' and A through the fourth NAND Gate to get (A.B')'. Pass both the output (A'.B)' and (A.B')' through the fifth NAND Gate to get our desired expression of XOR Gate ((A'.B)'.(A.B')')' = A'B + AB' (By De-Morgans Law).

Logic diagram

The Logical Diagram of the Following Expression is shown below

XOR Gate from NAND Gate
XOR Gate from NAND Gate

Conclusion

The use of NAND Gates to achieve the logical XOR operations demonstrates the efficiency, usability and adaptability of NAND Gates in simplifying circuit design and also provides valuable insights into the fundamental principles of digital electronics. With just five NAND gates, we can construct XOR gate. This process also involves the application of De Morgan’s law to convert the expressions. It shows how a logic function can be simplified using universal gates, reducing the complexity and cost.


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