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Chapter 1 : Introduction

Introduction arrow_upward

  • Digital electronics represent signals by discrete bands of analog levels, rather than by a continuous range.

  • What is Signal? arrow_upward

  • Signal is a function that conveys information about the behavior or attributes of some phenomenon.

  • Types of Signal arrow_upward

  • There are two types of signal:
    • Analog Signal
    • Digital Signal

    Analog Signal arrow_upward

  • Analog signal is defined as voltage or current whose size is proportional to the quantity it represents.
  • Analog Signal is continuous in nature and has infinite set of possible values.
  • Sound, Velocity, Weight, Pressure and Temperature etc. are analog in nature.

  • Digital Signal arrow_upward

  • A digital signal is a physical signal that is a representation of a sequence of discrete values (a quantified discrete-time signal).
  • The term digital signal can refer to either of the following:
    • Any continuous-time waveform signal used in digital communication, representing a bit stream or other sequence of discrete values.
    • A pulse train signal that switches between a discrete number of voltage levels or levels of light intensity, also known as a line coded signal or baseband transmission.

    Digital Techniques arrow_upward

  • Digital techniques have also replaced a lot of older analog circuits such as radios, TV sets.
  • Digital techniques are applied in many diverse areas such as telephony, data processing, radar, navigation, military system, medical instrumentation and process control.
  • Digital electronics involves system in which there are only two possible states that are represented by voltage levels.
  • In digital system two states are used to represent numbers, symbols and characters.

  • Analog System arrow_upward

  • In an analog system, the quantity can vary over a continuous range of values.
  • For example:

  • The amplitude of the output signal to the speaker in radio receiver can have any value between zero and its maximum limit.
  • Commonly used analog systems are TV Receiver, Telephone system and Magnetic tape recording.

  • Digital System arrow_upward

  • Digital system consists of devices designed to handle physical quantities that are represented in digital form.
  • Digital computers, calculators, digital watches and traffic signal controller are example of digital system.

  • Advantages of Digital System arrow_upward

  • Digital systems are easy to design.
  • Information can be stored very easily.
  • Digital circuits are less affected by noise.
  • More digital circuitry can be fabricated on IC chips as compared to analog circuit.

  • Digital Circuits arrow_upward

  • Digital circuits are the foundation of digital computers and automated control system.
  • In digital circuits, two voltage levels represent the two binary digits, 1 and 0 and are designed to produce output voltages that fall within the prescribed 0 and 1 voltage ranges.
  • Figure represents a typical digital circuit with input  and output
  • The output is shown in two different input signal waveforms.
  • Vout is same for both input waveforms, while they differ in their exact voltage levels.

  • Logic Circuits arrow_upward

  • The way in which a digital circuit responds to an input is known as the circuit’s logic.
  • Every digital circuit obeys a certain set of logic rules, thus digital circuits are also known as the logic circuits.
  • Logic circuits are generally composed of digital gates.
  • Combinations of gates form a circuit known as digital circuit.

  • Digital Integrated Circuits arrow_upward

  • All the digital circuits used in modern digital systems are integrated circuits.
  • Several IC fabrication technologies are used to produce digital ICs. The most common are TTL, CMOS, ECL, RTL,  etc.

  • Digital Computers arrow_upward

  • Computer is a system of hardware that performs arithmetic operations and manipulates data.
  • In computer, each unit performs specific functions and all units function together to carry out instructions in the program.
  • Figure shows major parts of a digital computer:
  • The major functions of each unit are:

  • Input Unit:
    • This unit is used to feed information into the computer system.
  •  Memory Unit:
    • This unit stores the instruction and data received from the input unit.
    • It stores the results of arithmetic operations received from the arithmetic unit.
    • It also supplies information to the output unit. 
  • Control Unit
    • This unit takes instruction from the memory unit one at a time and decodes them.
  • Arithmetic Unit
    • All arithmetic calculations and logic decisions are performed by this unit, and computation results are then stored in the memory.
  • Output Unit
    • It takes information from the memory unit and prints out displays or shows the information to the user or operator.

    Thank You from Kimavi arrow_upward

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