Encyclopedia
The field of
electronics comprises the study and use of systems that operate by controlling the flow of
electrons in devices such as
thermionic valves 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
Electronic systems are used to perform a wide variety of tasks. The main uses of electronic circuits are:
1. the controlling and processing of information
2. the conversion to/from and distribution of
electric powerBoth 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 . These devices take signals/information from external sources in the physical world and convert those signals/information into current/voltage or digital 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 that transform current/voltage signals back into useful physical form .
For example, a
television set contains these 3 parts. The telvision's input transforms a broadcast signal 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.
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 . Components may be packaged singly or in more or less complex groups as integrated circuits .
Active components are sometimes called
devices rather than components.
Types of circuits
Analog circuits
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 are 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 are constructed of digital circuits.
Digital Signal Processors are another example.
Building-blocks:
Highly integrated devices:
Mixed-signal circuits
Mixed-signal circuits refers to integrated circuits 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
liquid cooling for computers. 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 .
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 to extremely complex and sophisticated such as Automatic Test Equipment.
Computer aided design
Today's electronics engineers have the ability to design circuits using premanufactured building blocks such as
power supplies,
resistors,
capacitors,
semiconductors , and
integrated circuits.
Electronic design automation software programs include
schematic capture programs such as 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 starting with point to point wiring using tag boards attached to chassis, through printed circuit boards and ending with highly integrated circuits.
Some of the methods previously used are:
Branch pages
See also
External links
-
-
- DOE 1998 Electrical Science, Fundamentals Handbook, 4 vols.
- Directory of Electronics Projects.
-
-
