## EXAMPLE FOR WEEK 19

The following example is related to the work covered in WEEK 19.

The question was:-Try to draw the circuit for an EXCLUSIVE NOR Gate Circuit. Not the one for EXCLUSIVE OR followed by an inverter please!!!! Hint: work out the truth table for a two input circuit as we did above, and then implement it using gates.

The above circuit is supposed to implement an EXCLUSIVE NOR gate. The TRUTH table shown below is the starting point for the circuit design.

```B    A  OUTPUT
0    0    1
0    1    0
1    0    0
1    1    1
```
The output is a 1 only when A or B are the same. The two cases for a TRUE output are A = 0 and B = 0; A = 1 and B = 1. This suggests a way of making the circuit, AND A to B for one case. AND NOT A to NOT B for the other case. The two cases are OR'd together to give the required circuit. The TRUTH table shows how circuit operation is calculated in sections. The NOT A and NOT B columns are included to make the calculations easier
```B  NOT B  A  NOT A   X    y  x+y = OUTPUT
0    1    0    1     1    0      1
0    1    1    0     0    0      0
1    0    0    1     0    0      0
1    0    1    0     0    1      1
```
The circuit to implement the above looks like this.