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BASIC KNOWLEDGE - ELECTRONIC COMPONENTS Introduction to electronic compontents: Active vs. passive components

From Florian Richert |

One key factor that differentiates types of electronic components from each other is whether they are passive or active. However, many people are unsure of exactly what that difference entails. This article is here to help.

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Active and passive components of power electronics systems.
Active and passive components of power electronics systems.
(Source: Public Domain / Unsplash)

The key difference between active and passive components

Electronic components are categorized as active or passive depending on the functions they are able to perform. In a nutshell, active components can, generally speaking, inject power into a circuit and are capable of electrically controlling and amplifying the flow of electrical current, whereas passive components cannot.

Unlike active components, passive components either consume or store energy. A simple way to test whether a component is active or not is to measure the difference be-tween its input and output signals. If there is a decline in power, the component is passive. If the signal is amplified, it is active.

All electronic circuits must contain at least one active component, and most electronic devices contain both active and passive components.

Active components and their functions

Active components require a source of energy, typically in the form of a direct current, in order to perform their specific function. They are able to manipulate the flow of electricity in some way. Most active components consist of semiconductor devices, such as diodes, transistors and integrated circuits.

  • Transistor: Mostly used for amplifying electrical signals or as switching devices
  • Diode: Permits electricity to flow in one direction only
  • Integrated circuit (chips or microchips): multiple complex circuits on a circuit board; used to perform all kinds of tasks; still considered a component despite consisting of many other components
  • Display devices such as LCD, LED and CRT displays
  • Power sources such as batteries and other sources of alternating current (AC) or direct current (DC)

Passive components and their functions

Passive components can influence the flow of electricity running through them. For example, they can resist its flow, store energy for later use, or produce inductance. However, they cannot control or amplify electricity themselves.

The most common components and their functions:

  • Resistor: Resists the flow of electrical current in a circuit; used to lower voltage
  • Capacitor: Stores electrical energy electrostatically in an electric field (known as ‘charging’), and can release it later when needed
  • Inductor: Stores electrical energy in a magnetic field; allows direct current (DC) to flow through it, but not alternating current (AC)
  • Transducer: Converts an input signal from one type of energy into another type; sensors are a type of transducer that convert physical action/input into an electrical signal

Typical applications of active and passive components

We are surrounded by these tiny electronic elements in everyday life. They are hidden inside lights, sound systems, computers, phones, cars and many more. By definition, active components are found in every single electronic device, so they have countless use cases. Classic examples include any device with computing power (integrated circuits), devices with a built-in battery or display, and LED lights (light-emitting diodes).

When it comes to passive components, incandescent light bulbs are a great example of transducers in action - they convert electrical energy into light and heat energy. Loud-speakers use transducers to convert electrical input into mechanical output, causing the cones inside the speakers to vibrate, thereby generating sound waves that we can hear. Sensors are another type of transducer that have long been used in scientific research, and which are becoming increasingly ubiquitous through the ‘smartification’ of countless appliances and machines.

Other passive component use cases include microwave and radio frequency applications such as remote keyless entry systems, which rely on inductors. Antennas are also passive and are found in radios, GPS devices, satellites, wireless modems and routers, public transport and more.

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