Electronic component

Electronic component
Various components

An electronic component is a basic electronic element and may be available in a discrete form having two or more electrical terminals (or leads). These are intended to be connected together, usually by soldering to a printed circuit board, in order 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 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.



A component may be classified as passive or active. 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 performing circuit analysis use a more restrictive definition of passivity. When we are only concerned with the energy due to 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) although it may in reality be supplied by the DC circuit which we are ignoring. Then the analysis only concerns the so-called AC circuit, an abstraction which ignores the DC voltages and currents (and the power associated with them) present in the real-life circuit. This fiction, for instance, allows us to view an oscillator as "producing energy" even though in reality the oscillator consumes even more energy from a power supply, obtained through the DC circuit which we have chosen to ignore. Under that restriction we define the terms as used in circuit analysis as follows:

  • Passive components are ones which cannot introduce net energy into the circuit they are connected to. 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 are unable to amplify (increase the power of a signal), although they may well increase a voltage or current such as is done by a transformer or resonant circuit. Among passive components are familiar two-terminal components such as resistors, capacitors, inductors, and transformers.
  • Active components rely on a source of energy (usually from the DC circuit, which we have chosen to ignore) and are usually able to inject power into a circuit although this is not part of the definition[1]. This includes amplifying components such as transistors, triode vacuum tubes (valves), and tunnel diodes.

Passive components can be further divided into lossless and lossy components:

  • Lossless components do not have a net power flow into or out of the component. This would include ideal capacitors, inductors, transformers, and the (theoretical) gyrator.
  • Lossy or dissipative components do not have that property and generally absorb power from the external circuit over time. The prototypical example is the resistor. In practice all non-ideal passive components are at least a little lossy, but these are typically modeled in circuit analysis as consisting of an ideal lossless component with an attached resistor to account for the loss.

Most passive components with more than two terminals can be described in terms of two-port parameters satisfying the principle of reciprocity, although there are some rare exceptions[2]. In contrast, active components (which have more than two terminals) generally lack that property.

Note that these distinctions only apply to components listed below which would be modeled as elements within circuit analysis. Practical items which act as transducers or have other connections to the outside world such as switches, cannot be subject to this form of classification since they defy the view of the electronic circuit as a closed system.


Terminals and connectors

Devices to make electrical connection

Cable assemblies

Cables with connectors or terminals at their ends


Components that can pass current ("closed") or break the flow of 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 - Electrically operated switch (mechanical, also see Solid State Relay below)
  • 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


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

  • 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
  • Heater - heating element
  • Resistance wire, Nichrome wire - wire of high-resistance material, often used as heating element
  • Thermistor - temperature-varied resistor
  • Humistor - humidity-varied resistor
  • Varistor, Voltage Dependent Resistor, MOV - Passes current when excessive voltage present

Protection devices

Passive components that protect circuits from excessive currents or voltages


Components that store and release electrical charge. Used for filtering power supply lines, for tuning resonant circuits, and for blocking DC voltages while passing AC signals, among numerous other uses.

  • Capacitor - fixed capacitance
    • Capacitor network (array)
  • Variable capacitor - Adjustable capacitance
    • Tuning capacitor - Variable capacitor for tuning a radio, oscillator, or tuned circuit
    • Trimmer capacitor - Small variable capacitor usually for internal adjustments
  • Varicap diode - AC capacitance varies according to the DC voltage applied.

Magnetic (inductive) devices

Electrical components that use magnetism


Components that use more than one type of passive component

Piezoelectric devices, crystals, resonators

Passive components that use piezoelectric effect

  • Components that use the effect to generate or filter high frequencies
    • Crystal - Is 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 effect
    • For piezo buzzers and microphones, see the Transducer class below

Power sources

Sources of electrical power

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 (see also Piezoelectric devices)
    • Loudspeaker - Magnetic or piezoelectric device to generate full audio
    • Buzzer - Magnetic 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)



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


Active components used for amplification.

Integrated circuits

Optoelectronic devices

Display technologies



Vacuum tubes (Valves)

Based on current conduction through a vacuum (see Vacuum tube)

Amplifying tubes

Optical detectors or emitters

Discharge devices

  • Gas discharge tube



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

Mechanical accessories



Standard symbols

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

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 would be classified as an active component since it relies on a source of power to operate.
  2. ^ Nonreciprocal passive devices include the gyrator (although as a truly passive component this exists more in theoretical terms, and is usually implemented using an active circuit) and the circulator used at microwave and optical frequencies

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