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Digital Logic Designs

Lecture # 3

Logic Gates

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Introduction

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  • Digital logic gates are the building blocks of digital circuits, performing basic logical functions and enabling the design of complex electronic systems. In this lecture, we’ll explore how combinations of logic gates can be utilized to create various digital systems and circuits.

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**Logic Gates**

  • Logic Gates are devices that perform basic logical functions based on Boolean algebra. The most common types of gates include:
  • - **OR Gate**: Outputs true if at least one input is true.
  • - **NOT Gate**: Outputs the inverse of the input.
  • - **NAND Gate**: Outputs false only if all inputs are true (NOT AND).
  • - **NOR Gate**: Outputs true only if all inputs are false (NOT OR).
  • - **XOR Gate**: Outputs true if an odd number of inputs are true.
  • - **XNOR Gate**: Outputs true if an even number of inputs are true.

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AND Gate

  • AND Gate: Outputs true (1) only if all inputs are true.
  • Truth Tables describe the behavior of these gates by listing all possible input combinations and their corresponding outputs.

A

B

A.B

0

0

0

1

0

0

0

1

0

1

1

1

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OR Gate

  • OR Gate: Outputs true if at least one input is true.
  • Truth Tables describe the behavior of these gates by listing all possible input combinations and their corresponding outputs

A

B

A+B

0

0

0

1

0

1

0

1

1

1

1

1

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NOT Gate

  • NOT Gate: Outputs the inverse of the input.
  • Truth Tables describe the behavior of these gates by listing all possible input combinations and their corresponding outputs

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A

A

0

1

1

0

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NAND Gate

  • **NAND Gate**: Outputs false only if all inputs are true (NOT AND).
  • Truth Tables describe the behavior of these gates by listing all possible input combinations and their corresponding outputs.

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A

B

A.B

0

0

1

1

0

1

0

1

1

1

1

0

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NOR Gate

  • **NOR Gate**: Outputs true only if all inputs are false (NOT OR).
  • Truth Tables describe the behavior of these gates by listing all possible input combinations and their corresponding outputs.

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A

B

A+B

0

0

1

1

0

0

0

1

0

1

1

0

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XOR Gate

  • **XOR Gate**: Outputs true if an odd number of inputs are true.
  • Truth Tables describe the behavior of these gates by listing all possible input combinations and their corresponding outputs.

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XNOR Gate

  • **XNOR Gate**: Outputs true if an even number of inputs are true.

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