Electronics

Electronics is a branch of science and technology that deals with the flow of electrons through nonmetallic conductors, mainly semiconductors such as silicon. It is distinct from electrical science and technology, which deal with the flow of electrons and other charge carriers through metal conductors such as copper. This distinction started around 1906 with the invention by Lee De Forest of the triode. Until 1950 this field was called "radio technology" because its principal application was the design and theory of radio transmitters, receivers and vacuum tubes.

The study of semiconductor devices and related technology is considered a branch of 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 whose intention is 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, resistors, diodes, transistors, etc.

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 two voltage levels labeled "Low"(0) and "High"(1). Often "Low" will be near zero volts and "High" will be at a higher level depending on the supply voltage in use. 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:

Logic gates
Adders
Binary Multipliers
Flip-Flops
Counters
Registers
Multiplexers
Schmitt triggers

Highly integrated devices:

Microprocessors
Microcontrollers
Application-specific integrated circuit (ASIC)
Digital signal processor (DSP)
Field-programmable gate array (FPGA)

Mixed Signal circuits

It is rare you will find a purely digital or analog circuit in our time. Even FM radios are reduced to integrated circuits that contain both analog and digital elements, and though personal computers are almost entirely digital, certain ways computers communicate with the outside world such as the D-SUB video port use analog. Many of the circuit elements previously mentioned are actually mixed signal devices and employ Analog-to-digital and/or Digital-to-analog conversion. These methods allow circuits to create binary (digital) numbers associated with analog values with varying resolution and approximate analog signals from digital numbers respectively. The Microcontroller is an example of a Mixed-signal integrated circuit which employs both analog and digital techniques. While the computing core is digital, the microcontroller can also deal with analog values by using analog-to-digital converters. Digital cameras are another example as the CCD (Charge Coupled Device) sensor used in most cameras are not digital, but rather analog. The digital portion of the camera is responsible for control, human interface and digital signal processing among other things.

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 water cooling. These techniques use convection, conduction, & radiation of heat energy.