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Tech Talk

Active & Passive Components - What Is The Difference Between The Two?

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The Two Types of Electronic Devices

Electronic elements that make up a circuit are connected together by conductors to form a complete circuit.

  • Active components

  • Passive components

Active Components

An active component is an electronic component which supplies energy to a circuit.

Common examples of active components include:

  • Voltage sources

  • Current sources

  • Generators (such as alternators and DC generators)

  • All different types of transistors (such as bipolar junction transistors, MOSFETS, FETs, and JFET)

  • Diodes (such as Zener diodes, photodiodes, Schottky diodes, and LEDs)

Voltage Sources

A voltage source is an example of an active component in a circuit. When current leaves from the positive terminal of the voltage source, energy is being supplied to the circuit. As per the definition of an active element, a battery can also be considered as an active element, as it continuously delivers energy to the circuit during discharging.

Current Sources

A current source is also considered an active component. The current supplied to the circuit by an ideal current source is independent of circuit voltage. As a current source is controlling the flow of charge in a circuit, it is classified as an active element.

Transistors

Although not as obvious as a current or voltage source – transistors are also an active circuit component. This is because transistors are able to amplify the power of a signal (see our article on transisors as an amplifier if you want to know exactly how).

Passive Components

A passive component is an electronic component which can only receive energy, which it can either dissipate, absorb or store it in an electric field or a magnetic field. Passive elements do not need any form of electrical power to operate.

As the name ‘passive’ suggests – passive devices do not provide gain or amplification. Passive components cannot amplify, oscillate, or generate an electrical signal.

Common examples of passive components include:

  • Resistors

  • Inductors

  • Capacitors

  • Transformers

Resistors

A resistor is taken as a passive element since it can not deliver any energy to a circuit. Instead resistors can only receive energy which they can dissipate as heat as long as current flows through it.

Inductors

An inductor is also considered as passive element of circuit, because it can store energy in it as a magnetic field, and can deliver that energy to the circuit, but not in continuous basis. The energy absorbing and delivering capacity of an inductor is limited and transient in nature. That is why an inductor is taken as a passive element of a circuit.

Capacitors

A capacitor is considered as a passive element because it can store energy in it as electricfield. The energy dealing capacity of a capacitor is limited and transient – it is not actually supplying energy, it is storing it for later use.

As such it is not considered an active component since no energy is being supplied or amplified.

Transformers

A transformer is also a passive electronic component. Although this can seem surprising since transformers are often used to raise voltage levels – remember that power is kept constant.

When transformers step up (or step down) voltage, power and energy remain the same on the primary and secondary side. As energy is not actually being amplified – a transformer is classified as a passive element.

Source: El;ectrical 4U.com