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A passive component is a module that does not require energy to operate, except for the available alternating current (AC) circuit that it is connected to. A passive module is not capable of power gain and is not a source of energy. A typical passive component would be a chassis, inductor, resistor, transformer, or capacitor.
Generally, passive components are not able to increase the power of a signal nor are they able to amplify it. However, they can increase current or voltage by an LC circuit that stores electrical energy from resonant frequencies or by a transformer that acts like an electrical isolator.
In the context of electronic technology, there are stricter guidelines for the term passive component. Electronic engineers view this term usually in correlation with circuit analysis, which involves methods of finding the currents through and the voltages across every component in the network.
An electronic circuit that is composed of just passive components is called a passive circuit. A module that is not passive is called an active component.
Passive components can be divided into two types:
The majority of passive components that have two terminals are usually defined as a two-port parameter, which is an electric circuit or module that has two pairs of terminals linked together by an electric network. Two-port parameters comply with the standards of reciprocity. A two-port network would be a transistor, electronic filters, or impedance matching networks. A transducer or switch would not be a two-port parameter because it is a closed system. Although active components typically have more than two terminals, they are not classified as a two-port parameter because they lack the properties.
Passive components that use circuit architecture would include inductors, resistors, voltage and current sources, capacitors, and transformers. Likewise, passive filter are comprised of four elementary linear elements that include an inductor, capacitor, resistor, and transformer. Some high-tech passive filters can have non-linear elements like a transmission line.