Components that cannot control current by another electrical signal and that cannot provide power gain to the circuit are called passive devices. Resistors, capacitors, inductors, transformers, and even diodes are all considered passive devices. These devices cannot control the flow of current (energy) in the circuit and need the help of active devices to function.
A passive device (or passive component), in electronics, is an electronic component that returns less energy to the circuit than it receives; the missing energy is converted into thermal energy, which tends to overheat the component.
Although passive components cannot amplify a signal with a gain greater than one, they can multiply a signal by a value less than one. They can also oscillate, phase shift, and filter signals. Some passive components also have the ability to store energy (taken from an active element) and release it later.
Differences between active and passive components
Finally, the main differences between active and passive electronic components:
- Active devices provide power to the circuit, while passive devices cannot provide power.
- Active devices can provide power amplification and passive devices cannot provide power amplification.
- Active devices can control the flow of current (energy) within the circuit, while passive devices cannot.