Page 28 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

Universal Gates
NAND and NOR gates are known as a universal gates because from this two gates all other gates can be
constructed.
1. NAND Gate:
NAND gate represents combination of AND gate followed by NOT gate. It represents complement of AND operation.
Schematic symbol of NAND gate and its truth table ares hown below :
The logic Expression is given as X= orX= (A·B)2

NAND gateas Universal gate
1 Implementing NOT gate
All NAND input pins connect to the input signal A gives an output A’.
2 Implementing AND gate
The AND is replaced by a NAND gate with its output complemented by a NAND gate inverter

3 Implementing OR gate
The OR gate is replaced by a NAND gate with all its inputs complemented by NAND gate inverters.

7 NOR Gate
NOR gate represents combination of OR gatefollowed by NOT gate.It represents complement of ORoperation.
Schematic symbol of NOR gate and its truth table are shown below.
The logic expression is given as X=(AnorB) orX =(A+B)’.
NOR gate as Universal gate.

1 Implementing NOT gate
All NOR input pins connect to the input signal A gives an output A`.

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CITS : E & H - Electronics Mechanic - Lesson 5 - 8