Circuit diagram in the context of Integrated circuit layout

A design is the concept or proposal for an object, process, or system. The word design refers to something that is or has been intentionally created by a thinking agent, and is sometimes used to refer to the inherent nature of something – its design. The verb to design expresses the process of developing a design. In some cases, the direct construction of an object without an explicit prior plan may also be considered to be a design, such as in arts and crafts. A design is expected to have a purpose within a specific context, typically aiming to satisfy certain goals and constraints while taking into account aesthetic, functional and experiential considerations. Traditional examples of designs are architectural and engineering drawings, circuit diagrams, sewing patterns, and less tangible artefacts such as business process models.

A schematic, or schematic diagram, is a designed representation of the elements of a system using abstract, graphic symbols rather than realistic pictures. A schematic usually omits all details that are not relevant to the key information the schematic is intended to convey, and may include oversimplified elements in order to make this essential meaning easier to grasp, as well as additional organization of the information.

For example, a subway map intended for passengers may represent a subway station with a dot. The dot is not intended to resemble the actual station at all but aims to give the viewer information without unnecessary visual clutter. A schematic diagram of a chemical process uses symbols in place of detailed representations of the vessels, piping, valves, pumps, and other equipment that compose the system, thus emphasizing the functions of the individual elements and the interconnections among them and suppresses their physical details. In an electronic circuit diagram, the layout of the symbols may not look anything like the circuit as it appears in the physical world: instead of representing the way the circuit looks, the schematic aims to capture, on a more general level, the way it works. This may be contrasted with a wiring diagram, which preserves the spatial relationships between each of its components.

A wiring diagram is a simplified conventional pictorial representation of an electrical circuit. It shows the components of the circuit as simplified shapes, and the power and signal connections between the devices.

A wiring diagram usually gives information about the relative position and arrangement of devices and terminals on the devices, to help in building or servicing the device. This is unlike a circuit diagram, or schematic diagram, where the arrangement of the components' interconnections on the diagram usually does not correspond to the components' physical locations in the finished device. A pictorial diagram would show more detail of the physical appearance, whereas a wiring diagram uses a more symbolic notation to emphasize interconnections over physical appearance.

In electrical engineering, electrical elements are conceptual abstractions representing idealized electrical components, such as resistors, capacitors, and inductors, used in the analysis of electrical networks. All electrical networks can be analyzed as multiple electrical elements interconnected by wires. Where the elements roughly correspond to real components, the representation can be in the form of a schematic diagram or circuit diagram. This is called a lumped-element circuit model. In other cases, infinitesimal elements are used to model the network in a distributed-element model.

These ideal electrical elements represent actual, physical electrical or electronic components. Still, they do not exist physically and are assumed to have ideal properties. In contrast, actual electrical components have less than ideal properties, a degree of uncertainty in their values, and some degree of nonlinearity. To model the nonideal behavior of a real circuit component may require a combination of multiple ideal electrical elements to approximate its function. For example, an inductor circuit element is assumed to have inductance but no resistance or capacitance, while a real inductor, a coil of wire, has some resistance in addition to its inductance. This may be modeled by an ideal inductance element in series with a resistance.

A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. The primary benefit of the circuit is its ability to provide extremely accurate measurements (in contrast with something like a simple voltage divider). Its operation is similar to the original potentiometer.

The Wheatstone bridge was invented by Samuel Hunter Christie (sometimes spelled "Christy") in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. One of the Wheatstone bridge's initial uses was for soil analysis and comparison.

In electrostatics, a perfect conductor is an idealized model for real conducting materials. The defining property of a perfect conductor is that static electric field and the charge density both vanish in its interior. If the conductor has excess charge, it accumulates as an infinitesimally thin layer of surface charge. An external electric field is screened from the interior of the material by rearrangement of the surface charge.

Alternatively, a perfect conductor is an idealized material exhibiting infinite electrical conductivity or, equivalently, zero resistivity (cf. perfect dielectric). While perfect electrical conductors do not exist in nature, the concept is a useful model when electrical resistance is negligible compared to other effects. One example is ideal magnetohydrodynamics, the study of perfectly conductive fluids. Another example is electrical circuit diagrams, which carry the implicit assumption that the wires connecting the components have no resistance. Yet another example is in computational electromagnetics, where perfect conductors can be simulated faster, since the parts of equations that take finite conductivity into account can be neglected.

A field-programmable gate array (FPGA) is a type of configurable integrated circuit that can be repeatedly programmed after manufacturing. FPGAs are a subset of logic devices referred to as programmable logic devices (PLDs). They consist of a grid-connected array of programmable logic blocks that can be configured "in the field" to interconnect with other logic blocks to perform various digital functions. FPGAs are often used in limited (low) quantity production of custom-made products, and in research and development, where the higher cost of individual FPGAs is not as important and where creating and manufacturing a custom circuit would not be feasible. Other applications for FPGAs include the telecommunications, automotive, aerospace, and industrial sectors, which benefit from their flexibility, high signal processing speed, and parallel processing abilities.

A FPGA configuration is generally written using a hardware description language (HDL) e.g. VHDL, similar to the ones used for application-specific integrated circuits (ASICs). Circuit diagrams were formerly used to write the configuration.

A clock generator is an electronic oscillator that produces a clock signal for use in synchronizing a circuit's operation. The output clock signal can range from a simple symmetrical square wave to more complex arrangements. The basic parts that all clock generators share are a resonant circuit and an amplifier.

The resonant circuit is usually a quartz piezo-electric oscillator, although simpler tank circuits and even RC circuits may be used.

The control grid is an electrode used in amplifying thermionic valves (vacuum tubes) such as the triode, tetrode and pentode, used to control the flow of electrons from the cathode to the anode (plate) electrode. The control grid usually consists of a cylindrical screen or helix of fine wire surrounding the cathode, and is surrounded in turn by the anode. The control grid was invented by Lee De Forest, who in 1906 added a grid to the Fleming valve (thermionic diode) to create the first amplifying vacuum tube, the Audion (triode).

A plate, usually called anode in Britain, is a type of electrode that forms part of a vacuum tube. It is usually made of sheet metal, connected to a wire which passes through the glass envelope of the tube to a terminal in the base of the tube, where it is connected to the external circuit. The plate is given a positive potential, and its function is to attract and capture the electrons emitted by the cathode. Although it is sometimes a flat plate, it is more often in the shape of a cylinder or flat open-ended box surrounding the other electrodes.

In electrical engineering, a node is any region or joining point on a circuit between two circuit elements. In circuit diagrams, connections are ideal wires with zero resistance. Whether "node" refers to a single point of junction or an entire equipotential region varies by the source.

"Node" is often used, especially in mesh analysis, to mean a principal node, which is distinct from the usage defined above. A principal node is a point in a circuit diagram where three or more connections meet. Principal nodes are important points of consideration in applying Kirchhoff's circuit laws, because conservation of current means current can split or combine at these points.

Open-source hardware (OSH, OSHW) consists of physical artifacts of technology designed and offered by the open-design movement. Both free and open-source software (FOSS) and open-source hardware are created by this open-source culture movement and apply a similar concept to a variety of components. It is sometimes, thus, referred to as free and open-source hardware (FOSH), meaning that the design is easily available ("open") and that it can be used, modified and shared freely ("free"). The term usually means that information about the hardware is easily discerned so that others can make it – coupling it closely to the maker movement. Hardware design (i.e. mechanical drawings, schematics, bills of material, PCB layout data, HDL source code and integrated circuit layout data), in addition to the software that drives the hardware, are all released under free/libre terms. The original sharer gains feedback and potentially improvements on the design from the FOSH community. There is now significant evidence that such sharing can drive a high return on investment for the scientific community.

It is not enough to merely use an open-source license; an open source product or project will follow open source principles, such as modular design and community collaboration.