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Electronics

2007 Schools Wikipedia Selection. Related subjects: Engineering

   The field of electronics comprises the study and use of systems that
   operate by controlling the flow of electrons (or other charge carriers)
   in devices such as thermionic valves (vacuum tubes) and semiconductors.
   The design and construction of electronic circuits to solve practical
   problems is an integral technique in the field of electronics
   engineering and is equally important in hardware design for computer
   engineering. All applications of electronics involve the transmission
   of either information or power. Most deal only with information.

   The study of new semiconductor devices and surrounding technology is
   sometimes considered a branch of physics. This article focuses on
   engineering aspects of electronics.

Overview of electronic systems and circuits

   Commercial digital voltmeter checking a prototype
   Enlarge
   Commercial digital voltmeter checking a prototype

   Electronic systems are used to perform a wide variety of tasks. The
   main uses of electronic circuits are:
    1. The controlling and processing of data.
    2. The conversion to/from and distribution of electric power.

   Both these applications involve the creation and/or detection of
   electromagnetic fields and electric currents. While electrical energy
   had been used for some time prior to the late 19th century to transmit
   data over telegraph and telephone lines, development in electronics
   grew exponentially after the advent of radio.

   One way of looking at an electronic system is to divide it into 3
   parts:
     * Inputs – Electronic or mechanical sensors (or transducers). These
       devices take signals/information from external sources in the
       physical world (such as antennas or technology networks) and
       convert those signals/information into current/ voltage or digital
       (high/low) signals within the system.

     * Signal processors – These circuits serve to manipulate, interpret
       and transform inputted signals in order to make them useful for a
       desired application. Recently, complex signal processing has been
       accomplished with the use of Digital Signal Processors.

     * Outputs – Actuators or other devices (such as transducers) that
       transform current/voltage signals back into useful physical form
       (e.g., by accomplishing a physical task such as rotating an
       electric motor).

   For example, a television set contains these 3 parts. The television's
   input transforms a broadcast signal (received by an antenna or fed in
   through a cable) into a current/voltage signal that can be used by the
   device. Signal processing circuits inside the television extract
   information from this signal that dictates brightness, colour and sound
   level. Output devices then convert this information back into physical
   form. A cathode ray tube transforms electronic signals into a visible
   image on the screen. Magnet-driven speakers convert signals into
   audible sound. [[MARS ELECTRONICS]]

Electronic devices and components

   An electronic component is any indivisible electronic building block
   packaged in a discrete form with two or more connecting leads or
   metallic pads. Components are intended to be connected together,
   usually by soldering to a printed circuit board, to create an
   electronic circuit with a particular function (for example an
   amplifier, radio receiver, or oscillator). Components may be packaged
   singly (resistor, capacitor, transistor, diode etc.) or in more or less
   complex groups as integrated circuits (operational amplifier, resistor
   array, logic gate etc). Active components are sometimes called devices
   rather than components.

Types of circuits

Analog circuits

   Hitachi J100 adjustable frequency drive chassis. Enlarge
   Hitachi J100 adjustable frequency drive chassis.

   Most analog electronic appliances, such as radio receivers, are
   constructed from combinations of a few types of basic circuits. Analog
   circuits use a continuous range of voltage as opposed to discrete
   levels as in digital circuits. The number of different analog circuits
   so far devised is huge, especially because a 'circuit' can be defined
   as anything from a single component, to systems containing thousands of
   components.

   Analog circuits are sometimes called linear circuits although many
   non-linear effects are used in analog circuits such as mixers,
   modulators etc. Good examples of analog circuits include vacuum tube
   and transistor amplifiers, operational amplifiers and oscillators.

   Some analog circuitry these days may use digital or even microprocessor
   techniques to improve upon the basic performance of the circuit. This
   type of circuit is usually called 'mixed signal'.

   Sometimes it may be difficult to differentiate between analog and
   digital circuits as they have elements of both linear and non-linear
   operation. An example is the comparator which takes in a continuous
   range of voltage but puts out only one of two levels as in a digital
   circuit. Similarly, an overdriven transistor amplifier can take on the
   characteristics of a controlled switch having essentially two levels of
   output.

Digital circuits

   Digital circuits are electric circuits based on a number of discrete
   voltage levels. Digital circuits are the most common physical
   representation of Boolean algebra and are the basis of all digital
   computers. To most engineers, the terms "digital circuit", "digital
   system" and "logic" are interchangeable in the context of digital
   circuits. In most cases the number of different states of a node is
   two, represented by two voltage levels labeled "Low" and "High". Often
   "Low" will be near zero volts and "High" will be at a higher level
   depending on the supply voltage in use.

   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
     * Adders
     * Binary Multipliers
     * flip-flops
     * counters
     * registers
     * multiplexers
     * Schmitt triggers

   Highly integrated devices:
     * microprocessors
     * microcontrollers
     * Application specific integrated circuit(ASIC)
     * Digital signal processor (DSP)
     * Field Programmable Gate Array (FPGA)

Mixed-signal circuits

   Mixed-signal circuits refers to integrated circuits (ICs) which have
   both analog circuits and digital circuits combined on a single
   semiconductor die or on the same circuit board. Mixed-signal 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 and thermal management

   Heat generated by electronic circuitry must be dissipated to prevent
   immediate failure and improve long term reliability. Techniques for
   heat dissipation can include heatsinks and fans for air cooling, and
   other forms of computer cooling such as water cooling. These techniques
   use convection, conduction, & radiation of heat energy.

Noise

   Noise is associated with all electronic circuits. Noise is generally
   defined as any unwanted signal that is not present at the input of a
   circuit. Noise is not the same as signal distortion caused by a
   circuit.

Electronics theory

   Mathematical methods are integral to the study of electronics. To
   become proficient in electronics it is also necessary to become
   proficient in the mathematics of circuit analysis.

   Circuit analysis is the study of methods of solving generally linear
   systems for unknown variables such as the voltage at a certain node or
   the current though a certain branch of a network. A common analytical
   tool for this is the SPICE circuit simulator.

   Also important to electronics is the study and understanding of
   electromagnetic field theory.

Electronic test equipment

   Electronic test equipment is used to create stimulus signals and
   capture responses from electronic Devices Under Test (DUTs). In this
   way, the proper operation of the DUT can be proven or faults in the
   device can be traced and repaired.

   Practical electronics engineering and assembly requires the use of many
   different kinds of electronic test equipment ranging from the very
   simple and inexpensive (such as a test light consisting of just a light
   bulb and a test lead) to extremely complex and sophisticated such as
   Automatic Test Equipment.

Computer aided design (CAD)

   Today's electronics engineers have the ability to design circuits using
   premanufactured building blocks such as power supplies, resistors,
   capacitors, semiconductors (such as transistors), and integrated
   circuits. Electronic design automation software programs include
   schematic capture programs such as EWB ( electronic work bench )or
   ORCAD or Eagle Layout Editor, used to make circuit diagrams and printed
   circuit board layouts.

Construction methods

   Many different methods of connecting components have been used over the
   years. For instance, in the beginning point to point wiring using tag
   boards attached to chassis were used to connect various electrical
   innards. Cordwood construction and wire wraps were other methods used.
   Most modern day electronics now use printed circuit boards or highly
   integrated circuits.

Branch pages

     * Digital electronics
     * Analogue electronics
     * Microelectronics
     * Fuzzy electronics
     * Electronic Devices and Circuits
     * Integrated circuit
     * Optoelectronics
     * Semiconductor
     * Semiconductor device

   Retrieved from " http://en.wikipedia.org/wiki/Electronics"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
