Electronics (Translation from the French)

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Electronics is a branch of applied physics concerning devices whose function depends on the flow of electrons.

The term "electronics" can also designate phenomena related to electrons.

We generally date the origin of electronics to the 1904 invention of the electronic tube.

Due to the success of electronic devices and their impact on everyday life, the general public often confuses electronics with cybernetics (automation), and information technology.

Definition

Electronics is a technical or engineering science concerning the study and design of devices capable of handling electrical signals, i.e. electrical currents or potentials (voltages) , information or energy carriers.

In this definition, the idea of information is considered in the widest sense: meaning any quantity (physical, such as temperature or speed, or abstract, such as sound, an image, or a code) that can change with time according to a previously undetermined law.

As with any automated system, well designed electronic systems comprise two parts:

The first is the operational part that manages the energy-carrying power signals (high currents);
The second is an information-processing part and manages the information-carrying signals (low currents).

In classical information-processing electronic systems, information is coded using current and voltage. Electronic applications can be subdivided according to the output they are intended to give: a processed signal or a command. The first group includes domains such as information technology, telecommunications, measurements (sample and storage of information), etc.

Command applications control the function of a natural or engineered system. Controlling generally implies the measurement of a controlling parameter, comparison of the measurement with a model and the generation of a correcting demand if an error is present. In this way a controller can be viewed as a succession of signal processing operations, taking us back to the general definition given above.

History

Throughout the 19th century, different possibilities presented by electricity, components and electronic applications were discovered, (some, with no obvious immediate applications nor industrial manufacturing techniques available, were only used in later years.)

Without electronics, and of course the electrical power supply it needs, life in our modern society would be very different.

Disciplines of electronics

Electronics is a family of disciplines that are distinguished by the type of signal, the type of application or the hierarchical level that the element in question occupies in its global system.

Types of signals

Analogue information signals

Detailed article: analogue electronics.

"Analogue electronics" is the discipline concerned with the processing of analogue signals, i.e. signals that evolve continuously with time and that are able to take any value within a continuous interval. Most physical systems are analogue because physical quantities usually evolve in a continuous fashion (for example, temperature).

Connection problems Connections remain the weak link not only for power transmission but also for low current signals.

Weak currents: As the contact points become progressively oxidised, they become unreliable or intermittent. This is a problem also encountered in electromagnetic relays. The voltage applied is too low to create an arc which would otherwise "clean" the contact. It follows the formation of a layer of oxidised metal. The problem can be remedied by using gold plated contacts and by locating the contacts in a vacuum enclosure

Digital information signals

Detailed article: digital electronics.

In the opposite sense, digital electronics concerns the processing of signals that take discrete values. As such, the number of values that these signals can take is limited. Digital signals are coded with binary numbers. In the simplest case, a digital signal can only take the values 1 or 0. Digital electronics are particularly useful for systems comprising a microprocessor or a microcontroller. For example, a computer is a machine that consists mainly of digital electronics.

Currently, digital electronics are tending to replace analogue electronics more and more, as they allow easier development of new circuits, better integration and more user flexibility. In applications for the general public, this movement towards digital electronics is particularly noticeable in the audio and video sectors (camcorders, television) where analogue electronics had long dominated the market - photography is a special case because the analogue signal acquisition was chemical and not electronic. On the other hand, it should not be forgotten that, as discrete values do not exist in a physical system, analogue electronic phenomena continue to be present in digital circuits, particularly at high frequencies. Additionally, certain functions such as measurement and amplification are intrinsically analogue and can never be digitised. In general, all sensors are analogue.

As digital signals are also discrete in time, a quartz oscillator (clock) is generally used to synchronise different parts of a circuit with each other. Circuits containing one (or more) clock(s) are called synchronous circuits. The frequency (or clock frequency) of a digital circuit, expressed in hertz (Hz), represents the number of times a value can change state per second. It is possible, however, to work asynchronously from a clock if the circuit function is organised such that the different components synchronise amongst themselves by exchanging control signals (sometimes called handshaking). This is called asynchronous electronics.

Mixed electronics

Equally, mixed electronics refers to systems in which digital and analogue signals coexist. Mixed electronics makes use of Analogue-Digital converters (ADC) and Digital-Analogue converters (DAC). These converters enable the transformation of an analogue signal into a digital signal and vice-versa, providing an interface between purely analogue modules (such as sensors) and purely digital modules.

For example, a digital-display thermometer samples the temperature (an analogue quantity), measures its value and codes it into a digital sequence which it then displays on a screen. In this example, the first two operations are executed by analogue modules, the third requires an analogue-digital conversion and the last is a digital process.

Power signals

Detailed article: power electronics.

Power electronics is a group of techniques concerned with the energy contained in electrical signals, as opposed to other electronic disciplines that are principally concerned with the information contained within these signals. The range of powers seen in power electronics varies from a few micro Watts to several Megawatts.

Power electronics is based on devices that allow electrical energy to be transformed into other forms of energy (converters) and transducers (usually turbines and electric motors). Power electronics is used in the domestic and industrial electrotechnology field of application, where it replaces older electromechanical solutions.

Hierarchy of object in question

Certain disciplines of electronics are defined according to the place occupied by the device in the hierarchy of the electronic system, instead of according to its application.

Physics of components

A component, or an electronic device, is found at the lowest level of the system. "Physics of components" is the branch of electronics concerned with the design and study of elementary electronic components. It is related to technological know-how, which covers all the knowledge and tools necessary to manufacture a component. This is known as "electronic technology". The subjects of electronic technology and physics of electronic components essentially call for competency in basic sciences such as the physics of solids and chemical processes. Even though these activities are vital for electronics, they have little to do with the signal processing aspects of electronics. Rather, basic physics should be considered as a first step towards the applied science needed for the study of electronics. The basic components of electronics are the transistor, the resistor, the capacitor, the diode, etc.

Electronic engineering

An electronic circuit is the principle element studied in electronic science. An electronic circuit is a system that includes several interrelated electronic components. The word circuit comes from the fact that the processing is done by electric currents circulating in the interconnected components. "Circuit theory" is the discipline concerned with the study of the properties of electronic circuits. "Electronic circuit design" is the discipline that studies the methodology enabling the creation of a particular processing function from an electronic circuit. Modern electronic systems comprise hundreds of millions of elementary components. For this reason, electronic circuit design is concerned only with the creation of relatively simple functions (or modules) requiring a few tens of components.

Size of electronic circuits

The preceding group can be sub-classified according to the size of the electronic circuit being considered.

Electronic vacuum tubes

Detailed article: Electronic tube.

As its name indicates, this refers to vacuum tubes, or electronic tubes used as active elementary components (vacuum diodes, triodes, tetrodes, pentodes...). They are rarely used today except in the form of cathode tubes for television receivers and for certain components in very powerful radio transmitters. Even these are now disappearing. Vacuum tubes are still used in audio applications, notably for guitar amplifiers.

In their simplest configuration (diode), vacuum tubes consist of two electrodes, called the cathode and the anode, installed in a glass tube in which a vacuum has been created. The cathode is heated by a heating element, creating an electron "cloud" close to the cathode. When the electronic circuit to which the tube is connected creates a positive potential difference between the anode and cathode, an electric current (of electrons) is produced between the cathode and the anode (this is called a cathodic current). Metal gauzes can be inserted between the cathode and the anode. The cathodic current can be controlled by modulating the potential applied to these metal gauzes. Tubes equipped with a gauze are called triodes (three electrodes).

The design of vacuum tubes makes them extremely tolerant of overcharging. This advantage means the vacuum tube is still today a good candidate for extreme applications such as powerful radio transmitters (AM and FM) and X-ray emitters.

Lastly, light (one single photon) sent towards the cathode is sufficient to generate a cathodic current, even without the use of a heating element. "Dynodes" use this principle in cascade to detect light photons in certain medical imaging applications.

Discrete electronics

Detailed article : electronic circuits.

This refers to elementary individual or "discrete" (as opposed to integrated) components, often assembled on electronic cards. This type of electronic design is rarely used any more except for experimental designs or by hobby electronic scientists. Today it has been replaced with micro-electronics. On a modern electronic card, although the integrated circuits carry out the main functions, discrete components (generally resistors and capacitors) necessary for their operation are often still found

Micro-electronics

Detailed article: Micro-electronics.

This term comes from the process of miniaturising the basic electronic components. Miniaturisation started in the 1950s with the birth of semi-conductors and has today reached an extreme level. For 60 years the size of basic components has been reducing and has now attained the order of tens of nanometres. This progress has been made possible by advances in the procedures used to treat semi-conductor materials, particularly silicon, and has enabled several million basic components to be put onto a surface area of a few square millimetres. Micro-electronics is a term used to describe electronic systems using components micro- or nano- metres in size. The expression "integrated electronics" is a synonym of this term: it gives this image of a collection of components "integrated" on a single semi-conductor chip called an integrated circuit.

Nano-electronics and molecular electronics

Detailed articles : Nanoelectronics et Molecular electronics.

Otherwise, when talking about modern electronic systems, the prefix "micro" is becoming obsolete, in that components nanometres in size, and sometimes comparable to the size of molecules, are starting to appear. Hence the terms nanotechnology and molecular electronics are now used. Recent technical advances have enabled the design of components based on the properties of electrons and their spin: spintronics.

Microsystems

Detailed article: Microsystems.

With the progress in micro- and nano- technologies, we are seeing the merging of systems belonging to different technical domains (mechanical, thermal, optical) with electronic systems and circuits. These amalgamations are often called "multi-domain signal processing systems" or "multi-domain systems". Advanced silicon manufacturing processes are at the origin of this progress, which allows the creation of 3-dimensional structures on the same crystal of silicon as the electronic circuit. This proximity allows the interaction of processes that traditionally take place in different domains, and for signals of different physical nature (thermal, mechanical, optical...) to coexist in the same system. As such, since the 1990s, electromechanical micro-systems (EMMS) have been produced and used in large quantities.

Basic theory

Mathematical methods

Several tools exist to enable modelling of a circuit's electronic properties. As examples, we can cite the fundamental principles of electricity and electromagnetism (Ohm's Law, Gauss' Theory, Faraday's Law), models of the behaviour of semi-conductor materials (P-N junctions, the transistor effect, the avalanche effect) and mathematical and statistical tools (complex numbers, Fourier transform, Gauss's Law).

Simulation of electronic circuits, which can sometimes be complex and costly, is an advanced and widely used procedure. Certain software packages can handle numerous parameters, for example temperature or electromagnetic field strength.

Noise, electromagnetic interference, heat dissipation

Detailed article : Electromagnetic interference.

As for any system, an electronic circuit interacts with its immediate environment and therefore can generate noise or can have its function disturbed by a noisy environment. Electronic engineers aim to minimise these noise disturbances. They must work with parameters that change in a negative sense as technology advances: miniaturisation and integration of components and systems, increases in working frequency and widespread use of RFsystems.

Design methods

Modern electronic design is almost exclusively based on a few software packages coined Computer Assisted Design packages. This includes the creation of circuit diagrams, routing of wires and modelling. Complex integrated circuit design includes intermediate steps such as the creation of logic paths or the analysis of time delays. Programmable electronic components (microprocessors, FPGAs, DSP) move design activities further into the domain of information technology: they bring flexibility and lower costs.

Manufacturing methods

The manufacture of printed circuits has experienced much diversification since the 1980s. Although prototypes can still be produced using traditional methods, mass-production in factories that are becoming more and more complex and costly enables the production of high performance products at a reasonable cost. While the micro-electronics industry is requiring bigger investments to follow emerging technology, standard printed circuit industries are looking to improve their profitability (manufacture/assembly/test robots, GPAO, offshore relocation).

Test methods

The testing of an electronic circuit is an important step because complex systems are often involved, and they must be shown to perform accurately and reliably. Single unit tests are used to evaluate prototypes, whereas production line tests, which may be automated to some degree, are intended to repair manufacturing and/or assembly faults. Numerous tools exist for this important step: measuring equipment (multimeters, oscilloscopes, frequency analysers, etc), automatic measuring standards (JTAG, GPIB) and automated systems (nailboards, mobile sensors, specialised test benches).