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Electronic component
Discrete device in an electronic system

An electronic component is a fundamental part of an electronic system that influences electrons or their associated fields. Typically available as industrial products, these discrete components often feature electrical terminals or leads to connect within an electronic circuit designed for specific functions like amplifiers, radio receivers, or oscillators. While discrete components often contain semiconductor materials such as transistors, they can also be integrated into complex packages like integrated circuits or hybrid integrated circuits. Detailed specifications are provided in datasheets, distinguishing physical components from conceptual electrical elements.

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Classification

Components can be classified as passive, active, or electromechanic. The strict physics definition treats passive components as ones that cannot supply energy themselves, whereas a battery would be seen as an active component since it truly acts as a source of energy.

However, electronic engineers who perform circuit analysis use a more restrictive definition of passivity. When only concerned with the energy of signals, it is convenient to ignore the so-called DC circuit and pretend that the power supplying components such as transistors or integrated circuits is absent (as if each such component had its own battery built in), though it may in reality be supplied by the DC circuit. Then, the analysis only concerns the AC circuit, an abstraction that ignores DC voltages and currents (and the power associated with them) present in the real-life circuit. This fiction, for instance, lets us view an oscillator as "producing energy" even though in reality the oscillator consumes even more energy from a DC power supply, which we have chosen to ignore. Under that restriction, we define the terms as used in circuit analysis as:

  • Active components rely on a source of energy (usually from the DC circuit, which we have chosen to ignore) and usually can inject power into a circuit, though this is not part of the definition.4 Active components include amplifying components such as transistors, triode vacuum tubes (valves), and tunnel diodes.
  • Passive components cannot introduce net energy into the circuit. They also cannot rely on a source of power, except for what is available from the (AC) circuit they are connected to. As a consequence, they cannot amplify (increase the power of a signal), although they may increase a voltage or current (such as is done by a transformer or resonant circuit). Passive components include two-terminal components such as resistors, capacitors, inductors, and transformers.
  • Electromechanical components can carry out electrical operations by using moving parts or by using electrical connections.

Most passive components with more than two terminals can be described in terms of two-port parameters that satisfy the principle of reciprocity—though there are rare exceptions.5 In contrast, active components (with more than two terminals) generally lack that property.

Active components

Semiconductors

Transistors

Transistors were considered the invention of the twentieth century that changed electronic circuits forever. A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power.

Diodes

Conduct electricity easily in one direction, among more specific behaviors.

Integrated circuits

Integrated Circuits can serve a variety of purposes, including acting as a timer, performing digital to analog conversion, performing amplification, or being used for logical operations.

Programmable devices

Optoelectronic devices

Display technologies

Current:

Obsolete:

Vacuum tubes (valves)

A vacuum tube is based on current conduction through a vacuum (see Vacuum tube).

Optical detectors or emitters

Discharge devices

Obsolete:

Power sources

Sources of electrical power:

Passive components

Components incapable of controlling current by means of another electrical signal are called passive devices. Resistors, capacitors, inductors, and transformers are all considered passive devices.

Resistors

Pass current in proportion to voltage (Ohm's law) and oppose current.

  • Resistor – fixed value
    • Power resistor – larger to safely dissipate heat generated
    • SIP or DIP resistor network – array of resistors in one package
  • Variable resistor
    • Rheostat – two-terminal variable resistor (often for high power)
    • Potentiometer – three-terminal variable resistor (variable voltage divider)8
    • Trim pot – small potentiometer, usually for internal adjustments
    • Thermistor – thermally sensitive resistor whose prime function is to exhibit a large, predictable and precise change in electrical resistance when subjected to a corresponding change in body temperature.9
    • Humistor – humidity-varied resistor
    • Photoresistor
    • Memristor
    • Varistor, Voltage-dependent resistor, MOV – Passes current when excessive voltage is present
  • Resistance wire, Nichrome wire – wire of high-resistance material, often used as a heating element
  • Heater – heating element

Capacitors

Capacitors store and release electrical charge. They are used for filtering power supply lines, tuning resonant circuits, and for blocking DC voltages while passing AC signals, among numerous other uses.

Integrated passive devices

Integrated passive devices are passive devices integrated within one distinct package. They take up less space than equivalent combinations of discrete components.

Magnetic (inductive) devices

Electrical components that use magnetism in the storage and release of electrical charge through current:

Memristor

Electrical components that pass charge in proportion to magnetism or magnetic flux, and have the ability to retain a previous resistive state, hence the name of Memory plus Resistor.

Networks

Components that use more than one type of passive component:

Transducers, sensors, detectors

  1. Transducers generate physical effects when driven by an electrical signal, or vice versa.
  2. Sensors (detectors) are transducers that react to environmental conditions by changing their electrical properties or generating an electrical signal.
  3. The transducers listed here are single electronic components (as opposed to complete assemblies), and are passive (see Semiconductors and Tubes for active ones). Only the most common ones are listed here.

Antennas

Antennas transmit or receive radio waves

Assemblies, modules

Multiple electronic components assembled in a device that is in itself used as a component

Prototyping aids

Main article: Electronics prototyping

Electromechanical devices

Piezoelectric devices, crystals, resonators

Passive components that use piezoelectric effect:

  • Components that use the effect to generate or filter high frequencies
    • Crystal – a ceramic crystal used to generate precise frequencies (See the Modules class below for complete oscillators)
    • Ceramic resonator – Is a ceramic crystal used to generate semi-precise frequencies
    • Ceramic filter – Is a ceramic crystal used to filter a band of frequencies such as in radio receivers
    • surface acoustic wave (SAW) filters
  • Components that use the effect as mechanical transducers.

Microelectromechanical systems

Terminals and connectors

Devices to make electrical connection

Cable assemblies

Electrical cables with connectors or terminals at their ends

Switches

Components that can pass current ("closed") or break the current ("open"):

  • Switch – Manually operated switch
    • Electrical description: SPST, SPDT, DPST, DPDT, NPNT (general)
    • Technology: slide switches, toggle switches, rocker switches, rotary switches, pushbutton switches
  • Keypad – Array of pushbutton switches
  • DIP switch – Small array of switches for internal configuration settings
  • Footswitch – Foot-operated switch
  • Knife switch – Switch with unenclosed conductors
  • Micro switch – Mechanically activated switch with snap action
  • Limit switch – Mechanically activated switch to sense limit of motion
  • Mercury switch – Switch sensing tilt
  • Centrifugal switch – Switch sensing centrifugal force due to rate of rotation
  • Relay or contactor – Electro-mechanically operated switch (see also solid state relay above)
  • Reed switch – Magnetically activated switch
  • Thermostat – Thermally activated switch
  • Humidistat – Humidity activated switch
  • Circuit breaker – Switch opened in response to excessive current: a resettable fuse
  • Disconnector – Switch used in high- and medium-voltage applications for maintenance of other devices or isolation of circuits
  • Transfer switch – Switch that toggles a load between two sources

Protection devices

Passive components that protect circuits from excessive currents or voltages:

Mechanical accessories

Other

Obsolete

Standard symbols

Main article: Electronic symbol

On a circuit diagram, electronic devices are represented by conventional symbols. Reference designators are applied to the symbols to identify the components.

See also

Wikimedia Commons has media related to Electronic components.
  • Electronics portal

References

  1. "Definition of discrete component". https://www.pcmag.com/encyclopedia/term/discrete-component ↩

  2. Principles of VLSI and CMOS Integrated Circuits. S. Chand. 2016. ISBN 978-81-219-4000-9. 978-81-219-4000-9 ↩

  3. Passive and Discrete Circuits: Newnes Electronics Circuits Pocket Book, Volume 2. Elsevier. 23 June 2016. ISBN 978-1-4832-9198-7. 978-1-4832-9198-7 ↩

  4. For instance, a computer could be contained inside a black box with two external terminals. It might do various calculations and signal its results by varying its resistance, but always consuming power as resistance does. Nevertheless, it is an active component, since it relies on a power source to operate. ↩

  5. Nonreciprocal passive devices include the gyrator (though as a truly passive component, this exists more in theoretical terms, and is usually implemented using an active circuit)—and the circulator, which is used at microwave and optical frequencies /wiki/Gyrator ↩

  6. "13 Sextillion & Counting: The Long & Winding Road to the Most Frequently Manufactured Human Artifact in History". Computer History Museum. April 2, 2018. Retrieved 28 July 2019. https://www.computerhistory.org/atchm/13-sextillion-counting-the-long-winding-road-to-the-most-frequently-manufactured-human-artifact-in-history/ ↩

  7. Baker, R. Jacob (2011). CMOS: Circuit Design, Layout, and Simulation. John Wiley & Sons. p. 7. ISBN 978-1118038239. 978-1118038239 ↩

  8. Abernathy, Johanna. "Understanding Voltage Divider Circuits". QuarkTwin. Connelly Roth. Retrieved 22 April 2021. https://www.quarktwin.com/blogs/resistor/understanding-voltage-divider-circuits/389 ↩

  9. What is a Thermistor. U.S. Sensor Corp. http://www.ussensor.com/technical-info/what-is-a-thermistor ↩