The Difference Between Active and Passive Components

Within an electronic assembly or system, various electronic parts and components will work together to establish a complete circuit. All the components within a circuit can be divided into two groups, those of which are active and passive. While active components are those capable of providing energy to a circuit, passive components only receive energy. As both types of components serve different roles in the realm of circuit functionality, it is important to understand the differences between each and their common types.

Active components may come in many forms, popular variations including voltage and current sources, generators, transistors, and diodes. The voltage source is a common active component capable of supplying a circuit with current that leaves from its positive terminal. Due to this general definition, an electronic component such as a battery may be considered to be a type of voltage source due to its role in supplying a circuit with energy as it discharges. Current sources, meanwhile, are those that are independent of circuit voltage while supplying energy to the circuit. Because the current source is able to manage charge flow that enters into circuitry, it can be considered to be an active element. Transistors can come in many forms, common types including MOSFETS, FETs, JFETs, and bipolar junction transistors. While transistors differ from voltage and current sources in terms of their operations, they are still considered to be a type of active component because they are capable of amplifying signal power for the benefit of the circuit.

As stated before, passive components receive energy rather than supply it, and this is done through dissipation, absorption, or storage with the assistance of a magnetic or electric field. Passive components also do not require energy for their functionality, and they cannot affect the signals that pass through them through amplification, oscillation, etc. There are a number of passive components that are commonly found within circuitry, those of which include resistors, capacitors, inductors, and transformers.

Resistors are incapable of supplying a circuit with energy, instead managing the flow of current by limiting values and dissipating energy as heat. Inductors, meanwhile, are able to hold energy within a magnetic field, allowing it to be supplied and used when necessary. As energy is not supplied on a continuous basis, inductors are considered to be passive components rather than active elements. Capacitors are also able to store energy, though they keep current within an electric field as compared to inductors. Transformers are another passive component that is often confused with active elements, due to their ability to raise voltage levels. Because a transformer can only keep power constant, rather than supply energy as a source, it is passive in nature. When a transformer raises or lowers voltage levels, the amount of energy that enters and exits the component will remain constant. With active elements, power will typically be amplified.

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