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LOGIC GATES

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INTRODUCTION

A Gate is simply an electronic circuit which

operates on one or more input signals to

produce an output signal.

The interconnection of gates to perform a

variety of logical operations is called logic

design.

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A table which lists all the possible combinations

of input variables and the corresponding

outputs is called truth table.

NOT, AND & OR are the three basic gates.

NAND & NOR are the universal gates.

XOR & XNOR are the special purpose gates.

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NOT GATE (INVERTER)

It is a gate that accepts one input and

produces output which is complement of the

given input.

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THE NEGATION AND POLARITY

INDICATORS

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INVERTER TRUTH TABLE

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INVERTER OPERATION

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TIMING DIAGRAM

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APPLICATION EXAMPLE

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SWITCH REPRESENTATION

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THE AND GATE

An AND gate can have two or more inputs andperforms what is known as logical

multiplication.

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OPERATION OF AND GATE

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TRUTH TABLE

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3 INPUT AND GATE

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PULSED OPERATION

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LOGIC EXPRESSIONS FOR AND GATE

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APPLICATION EXAMPLE

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SWITCH REPRESENTATION

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THE OR GATE

An OR gate can have two or more inputs and

performs what is known as logical addition.

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OPERATION OF AN OR GATE

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TRUTH TABLE

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PULSED OPERATION

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APPLICATION EXAMPLE

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SWITCH REPRESENTATION

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UNIVERSAL GATES

NAND & NOR gates are known as universal

gates.

The reason being the only one type of gates,

either NAND or NOR are sufficient for the

realization of any logical expression.

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THE NAND GATE

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OPERATION OF A NAND GATE

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TRUTH TABLE

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PULSED OPERATION

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NEGATIVEOR EQUIVALENT OPERATION OF

A NAND GATE

A NAND gate can be used for an OR operation

that requires one or more LOW inputs to

produce a HIGH output. This aspect of NAND

operation is referred to as negative-OR.

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LOGIC EXPRESSIONS

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THE NOR GATE

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OPERATION OF A NOR GATE

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TRUTH TABLE

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PULSED OPERATION

NEGATIVE AND EQUIVALENT

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NEGATIVEAND EQUIVALENT

OPERATION OF A NOR GATE

A NOR gate can be used for an AND operation

that requires all LOW inputs to produce a HIGH

output. This aspect of NOR operation is referred

to as negative-AND.

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LOGIC EXPRESSIONS

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THE EXCLUSIVE-OR GATE

Standard symbols for an exclusive-OR (XOR for

short) gate are shown below:

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OPERATION

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TRUTH TABLE

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THE EXCLUSIVE-NOR GATE

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PULSED OPERATION

THE UNIVERSAL PROPERTY OF

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THE UNIVERSAL PROPERTY OF

NAND & NOR GATES

THE NAND GATE AS A UNIVERSAL

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THE NAND GATE AS A UNIVERSAL

LOGIC ELEMENT

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NAND LOGIC

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NAND LOGIC

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NAND LOGIC DIAGRAMS

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NOR LOGIC

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NOR LOGIC

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