Engineering:Electronic component

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An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not to be confused with electrical elements, which are conceptual abstractions representing idealized electronic components.

Electronic components have a number of electrical terminals or leads. These leads connect to other electrical components, often over wire, to create an electronic circuit with a particular function (for example an amplifier, radio receiver, or oscillator). Basic electronic components may be packaged discretely, as arrays or networks of like components, or integrated inside of packages such as semiconductor integrated circuits, hybrid integrated circuits, or thick film devices. The following list of electronic components focuses on the discrete version of these components, treating such packages as components in their own right.


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.[1] Active components include amplifying components such as transistors, triode vacuum tubes (valves), and tunnel diodes.
  • Passive components can't introduce net energy into the circuit. They also can't rely on a source of power, except for what is available from the (AC) circuit they are connected to. As a consequence they can't 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.[2] In contrast, active components (with more than two terminals) generally lack that property.

Active components



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.


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

  • Diode, rectifier, diode bridge
  • Schottky diode (hot carrier diode) – super fast diode with lower forward voltage drop
  • Zener diode – passes current in reverse direction to provide a constant voltage reference
  • Transient voltage suppression diode (TVS), unipolar or bipolar – used to absorb high-voltage spikes
  • Varicap, tuning diode, varactor, variable capacitance diode – a diode whose AC capacitance varies according to the DC voltage applied.
Various examples of Light-emitting diodes
  • Laser diode
  • Light-emitting diode (LED) – a diode that emits light
  • Photodiode – passes current in proportion to incident light
  • DIAC (diode for alternating current), Trigger Diode, SIDAC) – often used to trigger an SCR
  • Constant-current diode
  • Peltier cooler – a semiconductor heat pump
  • Tunnel diode - very fast diode based on quantum mechanical tunneling
  • Zener diode- a form of semiconductor diode in which at a critical reverse voltage a large reverse current can flow.

Integrated circuits

Optoelectronic devices

Display technologies


  • Filament lamp (indicator lamp)
  • Vacuum fluorescent display (VFD) (preformed characters, 7 segment, starburst)
  • Cathode ray tube (CRT) (dot matrix scan, radial scan (e.g. radar), arbitrary scan (e.g. oscilloscope)) (monochrome & colour)
  • LCD (preformed characters, dot matrix) (passive, TFT) (monochrome, colour)
  • Neon (individual, 7 segment display)
  • LED (individual, 7 segment display, starburst display, dot matrix)
  • Split-flap display (numeric, preprinted messages)
  • Plasma display (dot matrix)
  • OLED (similar to an LCD, but each pixel generates its own light, can be made flexible or transparent)
  • Micro-LED (similar to OLED, but uses inorganic LEDs instead of organic ones, does not suffer from screen burn-in, however it cannot be made flexible or transparent)


Vacuum tubes (valves)

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

Optical detectors or emitters

  • Phototube or photodiode – tube equivalent of semiconductor photodiode
  • Photomultiplier tube – phototube with internal gain
  • Cathode ray tube (CRT) or television picture tube (obsolete)
  • Vacuum fluorescent display (VFD) – modern non-raster sort of small CRT display
  • Magic eye tube – small CRT display used as a tuning meter (obsolete)
  • X-ray tube – generates x-rays

Discharge devices

  • Gas discharge tube
  • Ignitron
  • Thyratron


  • Mercury arc rectifier
  • Voltage regulator tube
  • Nixie tube

Power sources

Sources of electrical power:

  • Battery – acid- or alkali-based power supply.
  • Fuel cell – an electrochemical generator
  • Power supply – usually a main hook-up
  • Photovoltaic device – generates electricity from light
  • Thermoelectric generator – generates electricity from temperature gradients
  • Electrical generator – an electromechanical power source
  • Piezoelectric generator - generates electricity from mechanical strain
  • Van de Graaff generator - generates electricity from friction

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.


SMD resistors on a backside of a PCB

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)
    • 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.[5]
    • 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


Some different capacitors for electronic equipment

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.

  • Capacitor
    • Integrated capacitors
      • MIS capacitor
      • Trench capacitor
    • Fixed capacitors
      • Ceramic capacitor
      • Film capacitor
      • Electrolytic capacitor
        • Aluminum electrolytic capacitor
        • Tantalum electrolytic capacitor
        • Niobium electrolytic capacitor
        • Polymer capacitor, OS-CON
      • Supercapacitor (Electric double-layer capacitor)
      • Mica capacitor
      • Vacuum capacitor
    • Variable capacitor – adjustable capacitance
      • Tuning capacitor – variable capacitor for tuning a radio, oscillator, or tuned circuit
      • Trim capacitor – small variable capacitor for seldom or rare adjustments of LC-circuits
      • Vacuum variable capacitor
    • Capacitors for special applications
      • Power capacitor
      • Safety capacitor
      • Filter capacitor
      • Light-emitting capacitor
      • Motor capacitor
      • Photoflash capacitor
      • Reservoir capacitor
    • Capacitor network (array)
  • Varicap diode – AC capacitance varies according to the DC voltage applied

Magnetic (inductive) devices

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


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.


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.
  • Audio
    • Loudspeaker – Electromagnetic or piezoelectric device to generate full audio
    • Buzzer – Electromagnetic or piezoelectric sounder to generate tones
  • Position, motion
    • Linear variable differential transformer (LVDT) – Magnetic – detects linear position
    • Rotary encoder, Shaft Encoder – Optical, magnetic, resistive or switches – detects absolute or relative angle or rotational speed
    • Inclinometer – Capacitive – detects angle with respect to gravity
    • Motion sensor, Vibration sensor
    • Flow meter – detects flow in liquid or gas
  • Force, torque
    • Strain gauge – Piezoelectric or resistive – detects squeezing, stretching, twisting
    • Accelerometer – Piezoelectric – detects acceleration, gravity
  • Thermal
  • Magnetic field (see also Hall Effect in semiconductors)
  • Humidity
  • Electromagnetic, light
    • Photo resistor – Light dependent resistor (LDR)


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


A quartz crystal (left) and a crystal oscillator

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.
    • Ultrasonic motor – Electric motor that uses the piezoelectric effects
    • For piezo buzzers and microphones, see the Transducer class below

Terminals and connectors

Devices to make electrical connection

Cable assemblies

Electrical cables with connectors or terminals at their ends

  • Power cord
  • Patch cord
  • Test lead
2 different miniature pushbutton 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

Protection devices

Passive components that protect circuits from excessive currents or voltages:

Mechanical accessories



Standard symbols

Main page: 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


  1. 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 a resistance does. Nevertheless, it's an active component, since it relies on a power source to operate.
  2. 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
  3. "13 Sextillion & Counting: The Long & Winding Road to the Most Frequently Manufactured Human Artifact in History". April 2, 2018. Retrieved 28 July 2019. 
  4. Baker, R. Jacob (2011). CMOS: Circuit Design, Layout, and Simulation. John Wiley & Sons. p. 7. ISBN 978-1118038239. 
  5. What is a Thermistor. U.S. Sensor Corp.

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