Universal gates are logic gates that can implement any Boolean function without needing other gate types. The NAND and NOR gates are examples of universal gates. Using only NAND or NOR gates is advantageous in practice because they are economical to fabricate and are used in most integrated circuit logic families.

1. UNIVERSAL GATES

2. Universal Gate
 A universal gate is a gate which can implement any
Boolean function without need to use any other gate
type.
 The NAND and NOR gates are universal gates.
 In practice, this is advantageous since NAND and NOR
gates are economical and easier to fabricate and are the
basic gates used in all IC digital logic families.
2

3. NOR Gate
X Y Z
0 0 1
0 1 0
1 0 0
1 1 0
X
Y
YXYXZ 
3

4. NOR Gate as an Inverter Gate
X Z
0 1
1 0
X XZ 
XXX  (Before Bubble)
Equivalent to Inverter
4

5. NOR Gate as an OR Gate
X Y Z
0 0 0
0 1 1
1 0 1
1 1 1
X
Y
YXYXZ 
YX 
NOR Gate “Inverter”
Equivalent to OR Gate
5

6. NOR Gate as an AND Gate
X Y Z
0 0 0
0 1 0
1 0 0
1 1 1
Equivalent to AND Gate
X
Y
YXYXYXZ 
X
NOR Gate“Inverters”
Y
6

9. AND GATE USING NAND GATES