Active vs Passive Components
All electrical components can be divided into two main categories as active and passive devices. The categorization is based on components’ capability to produce energy to the circuit. If any component delivers the power to the circuit, it belongs to the active components category. If the component utilizes energy, it is called a passive element.
Any component that is capable of providing a power gain is called an active component. They inject power to the circuit, and can control the current (or energy) flow within the circuit. Any electronic circuit should contain at least one active component to operate. Some examples for active devices are battery, vacuum tubes, transistor and SCR (silicon controlled rectifier / thyristor).
Controlling the current flow in circuit may be helped by another small current or voltage. They are called current controlled devices (ex: Bipolar Junction Transistor) and voltage controlled devices (ex : Field Effect Transistor).
Components that cannot provide any power gain to the circuit are called passive devices. These devices are incapable of controlling the current (energy) flow in the circuit and need the help of active devices to operate. Some examples for passive devices are resistors, inductors and capacitors.
Although passive components cannot amplify a signal with a gain more than one, they can multiply a signal by a value less than one. They also can oscillate, phase shift and filter signals. Some passive components also have the capability to store energy (drawn from an active element) and release later. Example: capacitors and inductors.
What is the difference between active and passive components?
1. Active devices inject power to the circuit, whereas passive devices are incapable of supplying any energy
2. Active devices are capable of providing power gain, and passive devices are incapable of providing power gain.
3. Active devices can control the current (energy) flow within the circuit, whereas passive devices cannot control it.