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Guide to Electronic Terms And Acronyms

For those who are not electronics engineers

There are many terms that are unique to the industry, and a large number of abbreviations and acronyms. A few of the common ones are explained below.

Analogue Array.

Device containing a number of analogue circuit elements that can be configured to perform a variety of different functions.

Analogue or Analog.

System in which signals or information are represented by an infinitely variable quantity. In an electronic circuit this quantity is normally voltage or current. See also Digital.

ASIC

Application Specific Integrated Circuit. Electronic circuit on a single "chip" which has been custom developed specially for a particular application. See IC. and ASICs page

Binary.

Number system in base 2, which has only 0 and 1 as digits. This system is useful in electronics as numbers can be represented in digital form, with high or low voltages equating to the "0" or "1" state of each digit. With only 2 states it is easy to construct circuits to process binary numbers. A binary number, like a decimal number, has its most significant digit in the left-most position and the least significant at the right.
A "1" at the right-most position represents 1.
A "1" in the next column represents 2 to the power of 1 = 2
A "1" in the next column represents 2 to the power of 2 = 4
A "1" in the next column represents 2 to the power of 3 = 8
and so on. For example the binary number 1101 is equal to 8 + 4 + 1 = 13. See also Digital Logic

CMOS

Acronym for Complementary Metal Oxide Semiconductors. Many digital logic circuits use gates constructed of complementary (pairs of P-channel and N-channel) MOSFET transistors. This technology has the advantage of low power consumption compared to other topologies such as NMOS, ECL or TTL. Power is consumed only when a gate changes state.

Combinatorial Logic.

A logical function (see Digital Logic) having outputs that depend on the current state of the inputs. There may be any degree of complexity in processing the inputs to determine the output states, but a given set of inputs always produces the same output states. There is no element of memory in the logic device, so the previous states of the inputs have no effect on current output state. An example of a combinatorial logic function would be an adder, whose output is the arithmetic sum of two binary numbers presented simultaneously at its inputs. See also Sequential Logic.

CPLD

Complex Programmable Logic Device. These devices can be configured to perform a variety of combinatorial and sequential logic functions. They offer a high level of versatility.

Digital.

System in which all signals or information is represented by one of a finite number of discrete states. The most common form of digital representation is binary, in which each point in a circuit is in one of two possible states. These states are usually represented by high or low voltage. The exact levels of voltage or current in a digital circuit have no significance. See also Analogue

Digital Logic.

The electronic processing of information represented in digital form. Digital logic circuitry is used to perform arithmetic on binary numbers in a computer, to store data, to control processes and make decisions according to pre-determine rules. The basic element of a digital logic circuit is the Logic Gate. This device performs a simple operation on the logical states of its inputs and produces an output. An example is an AND gate. This device produces a binary 1 at its output if all its inputs are at a 1 state. The simplest gate is the NOT gate or inverter, which has one input and produces the opposite binary state at its output to that at its input. From combinations of these trivial functions, all the complexity of modern digital devices can be produced.

Diode

Electronic component with many applications.
See Semiconductor, Schottky Diode and LED

EMC

Electro-Magnetic Compatibility. The ability of systems to co-exist without interfering with each other. The interference may be either by radio waves emitted by one system or by noise transmitted through a common power supply connection. EMC studies two properties of systems, their susceptibility to interference generated externally and the emission of interference from the system.

FET

Field Effect Transistor. This is a transistor in which current flow between two of its terminals (drain and Source) is controlled by the voltage at a third terminal (gate). FETs are of either P-channel or N-Channel construction. P-channel devices have increasing current flow as the gate becomes more negative with respect to the source. N-channel devices have increasing current flow as the gate becomes more positive. The parameter specifying whether a transistor is N-channel or P-channel is know as the device polarity. There are two main types of FET. MOSFETs, in which the gate is insulated from the other terminals and JFETs in which there is a diode junction (see Semiconductor) between the gate and the channel which carries current between the other terminals.

FPGA

Field Programmable Gate Array. This device can be configured to perform a large variety of digital logic functions. Its function can be defined by programming. The device is programmed by the user. These devices are often large and complex.

Heatsink

Device designed to remove heat, usually from an electronic component. A heatsink may take the form of a block of metal with fins on it. The component to be cooled is placed in thermal contact with the metal block. The fins allow heat to be transferred to the surrounding air. Other types of heatsink may be quite sophisticated, some use a coolant fluid which is circulated through the heatsink and cooled remotely.

IC

Integrated Circuit. An electronic circuit on a single "chip" of semiconducting material. ICs contain the essential circuitry at the heart of products from wrist watches to computers to motorcar's engine controllers. These devices allow complex circuits to be made cheaply, reliably and very small.

IIC

Inter-Integrated Circuit. A serial communication protocol invented by Philips. It is used to transmit data between ICs within a circuit, or piece of equipment. It uses 2 signal lines, clock and data, which are pulled high by resistors and pulled low by the transmitting device. The system usually has a master and one or more slave devices, although mult-master system are possible. The master generates a clock and initiates data transfer, sending a slave address and a read or write instruction. The data line is bi-directional and is also used by the receiving device to send an acknowledgement.

LED

Light Emitting Diode. This electronic semiconducting device produces light when an electric current is passed through it. LEDs are used in many display and indication applications. Following the development of LEDs that produce high levels of light in the full range of colours, they also perform more general illumination duties where their superior efficiency is a major advantage.

MOSFET

Metal Oxide Semiconductor Field Effect Transistor. This is a transistor in which current flow between two of its terminals (drain and Source) is controlled by the voltage at a third terminal (gate). MOSFETs are of either P-channel or N-Channel construction. P-channel devices have increasing current flow as the gate becomes more negative with respect to the source. N-channel devices have increasing current flow as the gate becomes more positive. The parameter specifying whether a transistor is N-channel or P-channel is know as device polarity. Most MOSFETs are manufactured using silicon and for these devices N-channel types require less silicon for a given voltage and current rating. MOSFETs are also available as either enhancement or depletion mode devices. Enhancement mode devices are in the off state with no potential difference between gate and source, current flow increases with gate potential. Depletion mode devices pass current with zero voltage between gate and source. A positive or negative gate voltage increase or decrease current (depending on device polarity). Low voltage power switching and control applications are dominated by N-channel enhancement mode MOSFETs.

PAL

Programmable Array Logic. These are devices, which can be configured to perform a variety of combinatorial logic functions. See also digital logic and PLAs.

PCB

Printed Circuit board. A Piece of flat, often rigid, material used to provide mechanical mounting and electrical interconnectivity for electronic component. See PCB page.

PLA

Programmable Logic Array. These devices can be configured to perform a variety of combinatorial logic functions. They offer more versatility than the simpler PALs. See also digital logic.

Power Dissipation

In electronic engineering this term refers to the conversion of electrical power into heat. As power is dissipated in electronic components, the heat produces a temperature rise, which can damage or reduce the working life of the device. Measures, such as the use of a heatsink, may be required to prevent excessive temperature rise.

PWM

Pulse Width Modulation. A method to control the mean current or power in a load by energizing it for a given proportion of the time. The ratio of on time to off time is varied to produce the desired level. This allows efficient operation with minimal power dissipation in the controller compared with linear control, which attempts to regulate the load continuously.

Schottky Diode.

A diode whose active junction is between a metal and a semiconductor rather than between P and N doped regions within the semiconductor.

Semiconductor.

This is too big a subject for us to do justice to it here but this is a brief overview. A semiconductor is a material having particular electrical properties. These properties include having an electrical resistivety between that of a conductor and an insulator. What is really important about semiconductors is that, by adding small amounts of impurities to regions of the material, they can be made into a variety of useful electronic devices.

The most basic semiconductor device is the diode. This is formed at the boundary between regions with different types of impurity. The boundary produces special electrical properties and is known as a junction. The diode passes current in one direction easily with a low voltage drop. If a voltage is applied with the opposite polarity, very little current flows. Due to the peculiar properties of the diode junction, even this humble device can be adapted to perform such varied tasks as detecting or emitting light, measuring temperature or generating microwaves.

Another hugely important semiconductor device is the transistor (see Transistor). Semiconductors form the basis of microprocessors, memories, amplifiers and almost all the active components in modern electronic products.

Sequential Logic.

A logical function (see Digital Logic) having outputs that depend on the current and previous states of the inputs. There is an element of memory in the logic device, so the previous states of input effect on output states. An example of a sequential logic function is a counter who's output depends on the number of transitions on its clock input since its reset input was last active. See also Combinatorial Logic.

Simulation.

This term, as it relates to electronic hardware design, refers to the use of a computer to predict the behaviour of a circuit under given conditions. In order to perform a simulation the computer programme must be given information about the circuit to be simulated, the behaviour of the components in the circuit and the signals and loads that will be presented to the circuit. The circuit information may be presented in the form of a schematic or as a textual description of the circuit called a net list. The behaviour of the components is described in a formal manor, this description is called a simulation model. The format of the model will depend on the simulation program being used, a common format is known as SPICE.

SPICE, SPICE Model

SPICE is a particular method of defining the behaviour of electronic components by specifying certain parameters. A SPICE Model is a set of SPICE parameter values for a specific component. It allows a simulator to predict the behaviour of that component as it interacts with other circuit elements. Many SPICE parameters are based on physical attributes of the component. Component suppliers often provide SPICE models for their devices. SPICE if one of several systems of component modelling. See simulation.

Transistor

3 Terminal electronic semiconductor amplifying device. Current flow through the device is controlled by a signal applied to one terminal. The transistor allows a relatively low power signal to control a relatively high power. The transistor is one of the fundamental building blocks of most electronic circuitry. There are two main varieties of transistor. The BJT (Bi-polar Junction Transistor) is predominantly controlled by current, whereas the FET is voltage controlled.