What is an Active device?

An active device is defined by its requirement for an external voltage to operate. These devices typically use this voltage to control the flow of signals and can include components like transistors, operational amplifiers, and other circuit elements that need power to function. This power is essential for the amplification and processing of signals, which is a core characteristic of active devices. They play a crucial role in various applications by increasing signal strength, enabling signal manipulation, and providing functionalities that passive devices cannot.

In contrast, devices that do not require voltage are considered passive and generally cannot amplify signals or control voltage and current. Such passive devices include resistors, capacitors, and inductors. Active devices specifically differ from these passive components by their dependence on an external power source, which empowers them to perform their roles in electronic circuits.