A Brief Introduction to Electronic Components

Like how proteins are the building blocks of life, electronic components are the building blocks of electronic products. A PCB is the skeletal structure that is designed to compactly accommodate these components, hold them together, and establish robust interconnections to achieve the intended outputs.

Some of the most commonly used electronic components are resistors, capacitors, inductors, diodes, LEDs, transistors, ICs, and connectors. These components usually have leads/terminals and are available in specific standardized packages that the designer can choose to suit his application. SMT (Surface Mount Technology) and Through-hole are the two types of mounting techniques used to place components on a PCB.

Electronic devices can be divided into two major kinds: Passive and Active devices.

Passive devices

Passive devices do not provide gain, amplification, or directionality to a circuit but instead provide attenuation – the gain is always less than unity.

Here are some of the most common passive devices for your reference: resistors, capacitors, inductors, and transformers.


  • The resistors provide resistance to current flow in an electronic circuit. 
  • The voltage (V), current (I) and resistance (R) are related by Ohm’s law. i.e. V = IR.
  • Higher the resistance R, lower is the current I for a given voltage V across it.
  • The unit of resistance is Ohms (Ω).
  • Resistors dissipate electrical energy at I2R Watts or Joules/sec. 


  • Capacitors are electronic components that store electrical energy.
  • The capacitors are used to implement time delay for signals in a circuit.
  • The capacitors filter out the noise and help stabilize the supply voltage of a circuit when used between the point of interest and ground (or zero-volt reference).
  • The stored charge (Q), voltage (V), and capacitance (C) are related by

Q = CV

Since current I = dQ/dt (rate of change of charge),

Hence, I = C (dv/dt); therefore, if voltage across a capacitor is constant, there will be no current flow through the capacitor; and current will only flow across the capacitor if the voltage across it changing with time as for example an AC voltage.

That is why a capacitor is said to block DC signals and allows only AC signals to pass through it when used in the series of the path of the signal.

  • The energy stored in a capacitor C which has been charged to voltage V is given by

(1/2)CV2 Joules.

  • The unit of capacitance is Faraday (F).


  • Diodes are two-terminal semiconductor devices with an anode and a cathode.
  • The predominant feature of a diode is that they conduct electric current in only one direction.


  • Inductors are electronic components that store electromagnetic energy.
  • The unit of inductance L, is Henry (H).
  • Voltage V, across an inductor of inductance L, is given by

V = L (dI/dt)

That is, there is a voltage across inductor only if the current through it is changing;

DC current produces no voltage through an inductor.

  • If a current builds from 0 to I in an inductor, the energy stored in it equals

(1/2)LI2 Joules.

  • An ideal inductor has zero resistance. However, all real inductors have a definite, albeit, small value resistance.

Active devices

The electronic components that depend on an external power source for their operation are called active components. They can amplify signals and some may impart directivity to signals. Some of the active components are:


  • Transistors are three-terminal devices. They act as digital switches that are controlled by an electrical signal. They also amplify the AC signals and provide gain (>1).

ICs (Integrated Circuits):

  • Most of the ICs are active devices as they are composed of many diodes and transistors.

Read our article An Overview of Basic Electronic Components to learn more.

Electronic Component Part number & Datasheet

The electronic components are coded with their respective manufacturer part numbers. Each component has its own datasheet which explains its performance, features and specifications.  

Most of the components are available through major distributors:

  • Mouser
  • Digikey
  • Arrow
  • Avnet

Electronic Component Manufacturers

Here are some well-known component manufacturers:

  • Kemet
  • AVX
  • Vishay
  • Panasonic
  • TDK
  • Murata
  • Intel
  • Texas Instruments
  • Analog Devices
  • NXP
  • Maxim Integrated
  • Infineon
  • ROHM Semiconductor
  • Microchip Technology
  • TE Connectivity
  • Molex
  • Amphenol