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Exclusive-OR Gates

The exclusive-OR gate has a high output only when an odd number of inputs is high.

As shown in above circuit of Exclusive-OR gate, the upper AND gate gives output A’B and lower AND gate gives AB’ and both these output are given as input to OR gate whose output is given by Y=A’B+AB’

As shown in above circuit when both the inputs are low, both AND gates have low outputs, therefore final output Y is low.

If input A is low and B is high, the upper AND gate has high output, so the OR gate has high output as shown below.

Similarly, when A is high and B is low, we get final output high as shown below

If both A and B inputs are high, both AND gates have low outputs and the final output is low as shown below.

From the above discussion, the truth table of two input exclusive-OR gate can be given as follow.


From this truth table, we can say output is high when either A or B is high. When both the inputs are low or high, the output is low. This why circuit is known as exclusive-OR gate.

The above figure gives symbol of exclusive-OR gate.

Four Inputs Exclusive-OR Gate:

As shown in above circuit, a pair of exclusive-OR gate driving an exclusive-OR gate. If all inputs are low (A to D), input gates have low output, so the final gate has a low output.(verify from two input exclusive-OR gate truth table). If A to C are low and D is high, the upper gate has a low output, the lower gate has a high output, and the output gate has a high output.

Here is an important property of the above circuit’s truth table. Each ABCD input with an ODD number of 1s produces an output 1 as shown below truth table.

In second row of above truth table, when ABCD=0001, it has ODD number of 1s which gives output 1. When ABCD=0010, it produces output 1.

For EVEN number of input ABCD=0011, it produces output low.

Any Number of Inputs Exclusive-OR Gates:

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Comments on: "Exclusive-OR Gates" (2)

  1. can you show me the electric circuit for this logic gate

    • Yes, you may visit “http://www.falstad.com/circuit/e-xor.html” for the java applet(animation) of Ex-OR gate and you can play animation by changing different input and notice corresponding output. You need to install Java in ur pc. If u dont have java-plug in, u may download it here “http://java.com/en/download/index.jsp”. U can also learn about Ex-OR gate from “http://www.wisc-online.com/Objects/ViewObject.aspx?ID=DIG402” online learning object tutorial. For detail u may visit “http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/xor.html”

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