WHAT IS ELECTRONICS
Electronics is the branch of physics, 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. Thenonlinear 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 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,
specialist audio equipment 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
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:
§ Adders
§ Counters
Highly integrated devices:
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 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.
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 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
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)
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 captureprograms 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
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) andWaste Electrical and Electronic Equipment Directive (WEEE), which went into force in July 2006.
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