Both active and passive elements are part of electrical and electronic circuits. But various factor exists that differentiates the two. The crucial difference between active and passive elements is that an active component holds the ability to supply energy to the circuit.
As against, a passive component is not able to give the energy to the circuit in which they are employed.
Active components supply energy to the circuit by gaining the power from an external source such as a battery. However, passive components lack the ability to provide the power as they are designed only to either store or dissipate the power present in the circuit.
Here, in this article, you will get to know several differences between active and passive components. But before proceeding further, just put an eye over the contents that we are going to discuss here.
Content: Active Vs Passive Elements
Comparison Chart
| Parameter | Active Elements | Passive Elements |
|---|---|---|
| Basic | It provides power to the circuit. | It stores and dissipates power present in the circuit. |
| Requirement of external source | Required | Not Required |
| Acts as | Generators | Attenuators |
| Current Controllability | Can control the current flowing through the circuit. | Do not exhibit current controllability. |
| Direction of operation | Unidirection | Bidirectional |
| Categorized as | Non-linear elements | Linear elements |
| Power gain | Provides power gain | Do not provide power gain |
| Examples | Diode, transistor, op-amp. | Resistor, capacitor and inductor. |
Definition of Active Elements
Active elements are those components present in the circuit those are able to provide power or energy to the circuit by extracting the power from an external source.
And the ability to supply the energy continues for an indefinite time period till the presence of external supply source.
As active elements provide the power to the circuit in which they are employed thus acts as generators. Also, these hold the ability to control the flow of current through the circuit.
The elements like a diode, transistor, op-amp etc. are known to be active components in any circuit. Let us have a look at the brief discussion of these components:
- Diode: Diodes are basically semiconductor material that is composed of p and n-type semiconductor materials. A diode is a two terminal device.
A diode is an active component that is used to direct the current that is flowing through the circuit by allowing conduction in a single direction only.
The figure below shows the symbol of a diode:
- Transistor: A transistor is a 3 terminal device that exhibits amplifying action. As we have discussed that active components utilize the power from an external source and supplies it to the circuit to which it is connected.
In a similar way, a transistor performs amplifying action of the current in the circuit.
The figure below represents the symbol of the transistor:
Basically, transistors are classified as BJT and FET.
Definition of Passive Elements
Passive elements are those circuit components that cannot produce energy in the circuit in which they are employed. But they can store or dissipate the power present in the circuit.
Also, passive elements do not need external electrical power for their operation. Along with that due to bidirectional nature, passive components can be connected in either direction in the circuit.
Due to their power storing and dissipating ability they function as attenuators.
Passive components are resistor, inductor and capacitor etc. Let us have a brief description of these components:
- Resistor: Resistors are those passive elements that when employed in any circuit possess the ability to restrict the current flowing through that circuit.
The quantity that measures the amount of restriction offered by resistors is known as resistance. And its unit is ohms.
The figure below represents a resistor R:
The resistance of a resistor is given as:
: V is the drop across the resistor and
I denote the current flowing through that particular resistor.
- Capacitor: A capacitor is an element that stores the electric charges flowing through it across the two capacitive plates.
Capacitance is the unit that determines the amount of charge stored by the capacitor. Its unit is farads. The figure shown below represents the symbol of a capacitor:
It is given as:
: Q represents the charge stored and
V represents the voltage across the plates of the capacitor.
- Inductor: Inductors are those elements that have the ability to store energy. But unlike capacitors, inductors store power in magnetic field form.
Till the time current flows through the circuit, energy gets stored within the turns of the coil.
Inductance is the unit used for measuring the magnetic field stored within the coil. Its unit is Henry. The figure below shows the symbol of inductor:
Inductance is given as:
: 𝜙 denotes the flux linking and
I denote the current flowing through the inductor.
Key Differences Between Active and Passive Elements
- The factor that generates a key difference between active and passive elements is that an active component requires an external power source in order to provide energy to the circuit.
While a passive component does not need an external power source as they are unable to supply power and can only store or transfer the power present in the circuit. - Active elements act as generators due to their power supplying ability. However, passive elements act as attenuators due to their absorbing tendency.
- Active components usually possess unidirectional behaviour. While passive components exhibit bidirectional nature.
- Active components are categorized as non-linear elements. Whereas, passive components fall under the category of linear elements.
- As active elements function as heat source thus can provide power gain. However, passive elements act as a heat sink and hence unable to provide power gain.
- Active elements when connected in any circuit shows controllability towards current flowing through the circuit. While passive elements are not actually designed to control current flow.
- The examples of active components are diode, transistor and op-amp etc. While the examples of passive components are resistor, capacitor and inductor.
Conclusion
So, from the above discussion we can conclude that despite being the part of the same circuit, both active and passive components have their own region of operation. Passive elements possess symmetricity because they put a similar effect on all the signals irrespective of their polarity.
But this condition is not applied in case of active elements as they exhibit asymmetricity, according to the type of component it is.