Electronic component

From Wikipedia, the free encyclopedia
  (Redirected from Discrete component)
Jump to: navigation, search
Various electronic components

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 two or more electrical terminals (or leads) aside from antennas which may only have one terminal. These leads connect, usually soldered to a printed circuit board, to create an electronic circuit (a discrete 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.

Classification[edit]

A component may 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[edit]

Semiconductors[edit]

Diodes[edit]

Various types of Light-emitting diode

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

Transistors[edit]

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.

Integrated circuits[edit]

Optoelectronic devices[edit]

Display technologies[edit]

Current:

Obsolete:

Vacuum tubes (valves)[edit]

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

Amplifying tubes

Optical detectors or emitters

Discharge devices[edit]

Obsolete:

Power sources[edit]

Sources of electrical power:

Passive components[edit]

Resistors[edit]

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.[3]
    • 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
  • Heaterheating element

Capacitors[edit]

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.

Magnetic (inductive) devices[edit]

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

Memristor[edit]

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[edit]

Components that use more than one type of passive component:

Transducers, sensors, detectors[edit]

  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[edit]

Antennas transmit or receive radio waves

Assemblies, modules[edit]

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

Prototyping aids[edit]

Electromechanical[edit]

2 crystalline type oscillators

Piezoelectric devices, crystals, resonators[edit]

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.

Terminals and connectors[edit]

Devices to make electrical connection

Cable assemblies[edit]

Cables with connectors or terminals at their ends

2 different tactile switches

Switches[edit]

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

Protection devices[edit]

Passive components that protect circuits from excessive currents or voltages:

Mechanical accessories[edit]

Other[edit]

Obsolete[edit]

Standard symbols[edit]

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 component.

See also[edit]

References[edit]

  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. ^ What is a Thermistor. U.S. Sensor Corp.