Electronics

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 called
electronic engineering.

The main uses of electronic circuits are the controlling, processing and
distribution of information, and the conversion and distribution of
electrical power. Both of these uses involve the creation or detection of
electromagnetic fields and electric currents.

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.

See also: computer engineering, electrical engineering, integrated circuit,
list of electronics topics, microelectronics, optoelectronics,
point-to-point construction, printed circuit board, semiconductor,
transducer, wire wrap

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)
   * Logic analyzer (Tests digital circuits)
   * Oscilloscope (Measures all of the above as they change over time)
   * Electrometer (Measures charge)

Interconnecting Electronic Components

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

Passive Components

   * resistor
   * capacitor
   * inductor
   * transformer
   * piezoelectric crystal
   * magnetic amplifier (toroid)

Active Components (solid-state)

   * diode
        o light emitting diode
        o photodiode
        o laser diode
        o Zener diode
        o Schottky diode
        o transient voltage suppression diode
        o variable capacitance diode
   * transistor
        o field effect transistor
        o bipolar transistor
        o IGBT transistor
        o Darlington transistor
        o photo transistor
   * other active components
        o triac
        o thyristor
        o unijunction transistor
        o varistor
        o Silicon Controlled Rectifier (SCR)

Active Components (thermionic)

   * thermionic valve
   * cathode ray tube
   * klystron
   * magnetron

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 etc.

   * radio antenna

Analog circuits

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

   * Analog computer
   * electronic amplifiers
   * electronic filters
   * electronic oscillators
   * electronic mixers
   * electronic power supply
   * impedance matchers
   * operational amplifiers

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.

   * logic gates
   * flip-flops
   * counters
   * registers
   * multiplexers
   * microprocessors
   * microcontrollers
   * dsp

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.

Noise

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

   * Shot noise in resistors.
   * Thermal noise in resistors.
   * White noise
   * Coloured noise

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