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LOGIC GATE

WHAT WE ARE GOING TO LEARN?

The Logic Gate.Analogue and Digital signal.Bit and Byte.Boolean Theorem.Description and Circuit analyses of different

types of logic Gate.

ANALOGUE SIGNAL

DIGITAL SIGNAL

BITS AND BYTES

• Bits, Bytes, Mega, Giga, Tera (explained)• 1 bit = a 1 or 0 (b)

4 bits = 1 nybble (?)8 bits = 1 byte (B)1024 bytes = 1 Kilobyte (KB)1024 Kilobytes = 1 Megabyte (MB)1024 Megabytes = 1 Gigabyte (GB)1024 Gigabytes = 1 Terabyte (TB)

BOOLEAN EXPRESSION

THE LOGIC GATE

A logic gate is an elementary building block of a digital circuit. Most logic gates have two inputs and one output. At any given moment, every terminal is in one of the two binary conditions low (0) or high (1), represented by different voltage levels.

KINDS OF LOGIC GATE

There are seven kinds logic gates:1. The AND gate.2. The OR gate.3. The NAND gate. 4. The NOR gate.5. The exclusive OR gate.6. The exclusive NOR. 7. The NOT gate and the Buffer.

BASIC LOGIC GATE

KINDS OF LOGIC GATE

AND GATE

The “AND” element has been compared to a number of switches in series

AND GATE

TRUTH TABLE OF AND GATE

ANALOGE CIRCUIT OF AND GATE

OR GATE

It is an element, which allows signals to pass from one of a number of inputs to a common output, without allowing any interaction among the inputs.

ANALOGUE CIRCUIT OF OR GATE

ANALOGUE CIRCUIT OF OR GATE

ANALOGUE CIRCUIT OF OR GATE

TRUTH TABLE OR GATE

A B C

0 0 0

0 1 1

1 0 1

1 1 1

NOT GATE

NAND GATE AND NOR GATE

• The NAND gate can be constructed by using an AND gate, and directly connecting its output to a NOT gate. The NOT gate inverts the output from the AND gate and, therefore, changes all output logic 1’s to logic 0’s and vice versa.

NAND GATE AND NOR

• The NOR gate. As the NOR gate can be constructed by using an OR gate whose output is directly connected to a NOT element. The NOT element negates (inverts) the output from the OR gate, changing all logic 1’s to logic 0’s and vice versa.

NAND GATE AND NOR

A B C E

0 0 0 1

1 0 0 1

0 1 0 1

1 1 1 0

A B C E

0 0 0 1

0 1 1 0

1 0 1 0

1 1 1 0

NAND GATE NOR GATE

THREE INPUT NAND GATE

Input OutputA B C Y F0 0 0 0 1

0 0 1 0 1

0 1 0 0 1

0 1 1 0 1

1 0 0 0 1

1 1 0 0 1

1 0 1 0 1

1 1 1 1 0

THREE INPUT NOR GATE

INPUT OUTPUTA B C Y F0 0 0 0 10 1 0 1 00 0 1 1 00 1 1 1 01 0 0 1 01 1 0 1 01 0 1 1 01 1 1 1 0

USES OF LOGIC GATE

• Pin out diagram of a 74266 Quad XNOR DIP-format IC

RECAPITULATION

The Logic Gate.Analogue and Digital signal.Bit and Byte.Boolean Theorem.Description and Circuit analyses of different

types of logic Gate.

QUESTION AND ANSWER

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