Electronics -is the branch of science, engineering and technology dealing with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies. The nonlinear
behaviour of active components and their ability to control electron
flows makes amplification of weak signals possible and is usually
applied to information and signal processing.
Similarly, the ability of electronic devices to act as switches makes
digital information processing possible. Interconnection technologies
such as circuit boards,
electronics packaging technology, and other varied forms of
communication infrastructure complete circuit functionality and
transform the mixed components into a working system.
Electronics is distinct from electrical and electro-mechanical
science and technology, which deals with the generation, distribution,
switching, storage and conversion of electrical energy to and from other
energy forms using wires, motors, generators, batteries, switches, relays, transformers, resistors and other passive components. This distinction started around 1906 with the invention by Lee De Forest of the triode, which made electrical amplification
of weak radio signals and audio signals possible with a non-mechanical
device. Until 1950 this field was called "radio technology" because its
principal application was the design and theory of radio transmitters, receivers and vacuum tubes.Today, most electronic devices use semiconductor components to perform electron control. The study of semiconductor devices and related technology is considered a branch of solid state physics, whereas the design and construction of electronic circuits to solve practical problems come under electronics engineering. This article focuses on engineering aspects of electronics.
Electronic devices and components
An electronic component is any physical entity in an electronic system used to affect the electrons or their associated fields in a desired manner consistent with the intended function of the electronic system. Components are generally intended to be connected together, usually by being soldered to a printed circuit board (PCB), to create an electronic circuit with a particular function (for example an amplifier, radio receiver, or oscillator). Components may be packaged singly or in more complex groups as integrated circuits. Some common electronic components are capacitors, inductors, resistors, diodes, transistors, etc. Components are often categorized as active (e.g. transistors and thyristors) or passive (e.g. resistors and capacitors).
Early electronic components
Vacuum tubes were one of the earliest electronic components. They dominated electronics until the 1950s. Since that time, solid state devices have all but completely taken over. Vacuum tubes are still used in some specialist applications such as high power RF amplifiers, cathode ray tubes, and some microwave devices.
Types of circuits
Circuits and components can be divided into two groups: analog and digital. A particular device may consist of circuitry that has one or the other or a mix of the two types.
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 include vacuum
tube and transistor amplifiers, operational amplifiers and oscillators.
One rarely finds modern circuits that are entirely analog. These days
analog circuitry may use digital or even microprocessor techniques to
improve performance. This type of circuit is usually called "mixed
signal" rather than analog or digital.
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 only outputs 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
Main article: Digital electronics
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. Most digital
circuits use a binary system with two voltage levels labeled "0" and
"1". Often logic "0" will be a lower voltage and referred to as "Low"
while logic "1" is referred to as "High". However, some systems use the
reverse definition ("0" is "High") or are current based. Ternary (with three states) logic has been studied, and some prototype computers made. 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:
Highly integrated devices:
- Microprocessors
- Microcontrollers
- Application-specific integrated circuit (ASIC)
- Digital signal processor (DSP)
- Field-programmable gate array (FPGA)
Main article: Thermal management of electronic devices and systems
Heat
generated by electronic circuitry must be dissipated to prevent
immediate failure and improve long term reliability. Techniques for heat
dissipation can include heat sinks 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
Main article: Electronic noise
Noise is associated with all electronic circuits. Noise is defined[1]
as unwanted disturbances superposed on a useful signal that tend to
obscure its information content. Noise is not the same as signal
distortion caused by a circuit. Noise may be electromagnetically or
thermally generated, which can be decreased by lowering the operating temperature of the circuit. Other types of noise, such as shot noise cannot be removed as they are due to limitations in physical properties.
Electronics theory
Main article: Mathematical methods in electronics
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 through 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.
Electronics lab
Main article: Electronics lab simulation
Due to the empirical
nature of electronics theory, laboratory experimentation is an
important part of the study of electronics. These experiments are used
to prove, verify, and reinforce laws and theorems such as Ohm's law, Kirchhoff's laws,
etc. Historically, electronics labs have consisted of electronics
devices and equipment located in a physical space, although in more
recent years the trend has been towards electronics lab simulation software, such as CircuitLogix, Multisim, and PSpice.
Computer aided design (CAD)
Main article: Electronic design automation
Today's electronics engineers have the ability to design circuits using premanufactured building blocks such as power supplies, semiconductors (such as transistors), and integrated circuits. Electronic design automation software programs include schematic capture programs and printed circuit board design programs. Popular names in the EDA software world are NI Multisim, Cadence (ORCAD),
Eagle PCB and Schematic, Mentor (PADS PCB and LOGIC Schematic), Altium
(Protel), LabCentre Electronics (Proteus), GEDA, KiCad and many others.Construction methods
Main article: Electronic packaging
Many different methods of connecting components have been used over the years. For instance, early electronics often used point to point wiring with components attached to wooden breadboards to construct circuits. Cordwood construction and wire wraps were other methods used. Most modern day electronics now use printed circuit boards made of materials such as FR4, or the cheaper (and less hard-wearing) Synthetic Resin Bonded Paper (SRBP,
also known as Paxoline/Paxolin (trade marks) and FR2) - characterised
by its light yellow-to-brown colour. Health and environmental concerns
associated with electronics assembly have gained increased attention in
recent years, especially for products destined to the European Union,
with its Restriction of Hazardous Substances Directive (RoHS) and Waste Electrical and Electronic Equipment Directive (WEEE), which went into force in July 2006.
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