Electronics is the study and use of electrical devices that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. The pure study of such devices is considered as a branch of physics, while the design and construction of electronic circuits to solve practical problems is part of the fields of electrical, electronic and computer engineering.

The main uses of electronic circuits are the controlling, processing and distribution of information, and the conversion and distribution of electric power. Both of these uses involve the creation or detection of electromagnetic fields and electric currents. More broadly, most electronics systems fall into the category of either control systems or communication systems.

While electricity had been used for some time to transmit data over telegraphs and telephones, the development of electronics truly began in earnest with the advent of radio. Today, electronic devices perform a much wider variety of tasks.

One way of looking at an electronic system is to divide it into the following parts:

1. Inputs - Electrical or mechanical sensors (or transducers), which take signals (in the form of temperature, pressure, etc.) from the physical world and convert them into current/voltage signals.
2. Signal processing circuits - These consist of electronic components connected together to manipulate, interpret and transform the signals.
3. Outputs - Actuators or other devices (also transducers) that transform current/voltage signals back into useful physical form.

Take as an example a television. Its input is a broadcast signal received by an antenna or fed in through a cable. Signal processing circuits inside the television extract the brightness, colour and sound information from this signal. The output devices are a cathode ray tube that converts electronic signals into a visible image on a screen and magnet driven audio speakers.

AC electronics frequencies are ultimately limited by a heat dissipation barrier at around 50 gigahertz and a plasma resonance barrier at approximately 1 terahertz. Instead of signals manifest in electrical currents, signals in polaritonics are manifest as admixtures of lattice vibrations and electromagnetic waves, and operate in the range of frequencies from 100 gigahertz to approximately 10 terahertz. Photonics, in which signals are manifest purely as electromagnetic waves propagating in non-dispersive media, operates at frequencies on the order of hundreds of terahertz, but is limited in functionality as compared to polaritonics or electronics. Polaritonics bridges the gap between electronics and photonics.

Electronic test equipment

• Ammeter, e.g. Galvanometer (Measure current)
• Ohmmeter, e.g. Wheatstone bridge (Measure resistance)
• Voltmeter (Measures voltage)
• Multimeter (Measures all of the above)
• Oscilloscope (Measures all of the above as they change over time)
• Logic analyzer (Tests digital circuits)
• Spectrum analyzer (SA) (Measures spectral energy of signals)
• Vector signal analyzer (VSA) (Like the SA but it can also perform many more useful digital demodulation functions)
• Electrometer (Measures charge)
• Frequency counter (Measures frequency)

Interconnecting electronic components

• electrical connectors, plugs and sockets etc.
• printed circuit boards
• integrated circuit
• point-to-point construction
• wire-wrap
• breadboard

Passive components

• fuse
• capacitor
• inductor
• magnetic amplifier (toroid)
• piezoelectric crystal
• polyswitch
• resistor
• varistor
• transformer

Active components (solid-state)

• diode
  • light-emitting diode
  • photodiode
  • laser diode
  • Zener diode
  • Schottky diode
  • transient voltage suppression diode
  • variable capacitance diode
• transistor
  • field effect transistor
  • bipolar transistor
  • IGBT transistor
  • Darlington transistor
  • photo transistor
• integrated circuit
  • digital
  • analogue
• other active components
  • triac
  • thyristor
  • unijunction transistor
  • Silicon Controlled Rectifier (SCR)
  • Field-emitter microtube

Active components (thermionic)

• thermionic valve
• cathode ray tube
• klystron
• magnetron

Display devices

• cathode ray tube
• liquid crystal display
• light-emitting diode
• nixie tube

Electromechanical sensors and actuators

• microphone
• loudspeaker
• strain gauge
• switch

Thermoelectric devices

• thermistor
• thermocouple
• thermopile
• Peltier cooler

Photoelectric devices

• light-dependent resistor
• photodiode
• photovoltaic cell (solar cell)

Antennae

• biconical
• Cassegrain
• elemental dipole
• feedhorn, waveguide
• magnetic dipole (loop)
• parabolic dish
• phased array
• radio antenna
• Yagi

Analog circuits

Most analog electronic appliances, such as radio receivers, are constructed from arrays of a few types of circuits.

• Analog computer
• Analog multipliers
• electronic amplifiers
• electronic filters
• electronic oscillators
• Phase-locked loops
• electronic mixers
• electronic power supply
• impedance matchers
• operational amplifiers
• comparators

Digital circuits

Computers, electronic clocks, and programmable logic controllers (used to control industrial processes) are constructed of digital circuits. Digital Signal Processors are another example.

Building-blocks:

• logic gates
• flip-flops
• counters
• registers
• multiplexers
• Schmitt triggers

Complex devices:

• microprocessors
• microcontrollers
• DSP
• Field Programmable Gate Array

Mixed-signal circuits

Mixed-signal circuits, also known as hybrid circuits, are becoming increasingly common. Mixed circuits contain both analog and digital components. analog to digital converters and digital to analog converters are the primary examples. Other examples are transmission gates and buffers.

Heat dissipation

Heat generated by electronic circuitry must be dissipated to improve reliability. Techniques for heat dissipation can include heatsinks and fans for air cooling, and other forms of computer cooling such as liquid cooling for computers .

Noise

Associated with all electronic circuits is noise. Types of noise include

• Shot noise in resistors.
• Johnson-Nyquist noise (Thermal noise) in resistors.
• White noise
• 1/f noise (pink noise, or flicker noise)

Electronics theory

• Mathematical Methods of Electronics
• Digital Circuits
• Analog Electronics

See also

• Electrical engineering
  • Integrated circuit
  • Optoelectronics
  • Point-to-point construction
  • Printed circuit board
  • Semiconductor
  • Semiconductor device
  • transducer
  • Wire wrap
  • Signal theory
• Computer engineering
  • Microelectronics
• Datasheet
• Mechatronics
• Electronics manufacturing
• List of electronics topics

External links

Tutorials and projects

• Electronics Infoline Directory for electronics projects
• Wikibooks Electronics
• Electronics tutorials.com
• Williamson Labs' Electronics tutorial
• Ian Purdie's Electronics tutorials
• Iguana Labs' Electronics Tutorials and Kits
• Electronic Meanings and Acronyms
• Lessons in Electric Circuits - A free series of textbooks on the subjects of electricity and electronics.
• Radio-Electronics.Com Free information and resources covering radio and electronics
• A hobbyist wiki

Some other good sites

• IEEE
• IEEE spectrum
• Electronix Express