# Electronic circuit design

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Electronic circuit design comprises the analysis and synthesis of electronic circuits.

## Methods

To design any electrical circuit, either analog or digital, electrical engineers need to be able to predict the voltages and currents at all places within the circuit. Linear circuits, that is, circuits wherein the outputs are linearly dependent on the inputs, can be analyzed by hand using complex analysis. Simple nonlinear circuits can also be analyzed in this way. Specialized software has been created to analyze circuits that are either too complicated or too nonlinear to analyze by hand.

Analogue electronics are electronic systems with a continuously variable signal, in contrast to digital electronics where signals usually take only two levels. The term "analogue" describes the proportional relationship between a signal and a voltage or current that represents the signal. The word analogue is derived from the Greek word ανάλογος (analogos) meaning "proportional". Electrical engineering is a technical discipline concerned with the study, design and application of equipment, devices and systems which use electricity, electronics, and electromagnetism. It emerged as an identified activity in the latter half of the 19th century after commercialization of the electric telegraph, the telephone, and electrical power generation, distribution and use.

A linear circuit is an electronic circuit which obeys the superposition principle. This means that the output of the circuit F(x) when a linear combination of signals ax1(t) + bx2(t) is applied to it is equal to the linear combination of the outputs due to the signals x1(t) and x2(t) applied separately:

Circuit simulation software allows engineers to design circuits more efficiently, reducing the time cost and risk of error involved in building circuit prototypes. Some of these make use of hardware description languages such as VHDL or Verilog. VHDL (VHSIC-HDL) is a hardware description language used in electronic design automation to describe digital and mixed-signal systems such as field-programmable gate arrays and integrated circuits. VHDL can also be used as a general purpose parallel programming language.

Verilog, standardized as IEEE 1364, is a hardware description language (HDL) used to model electronic systems. It is most commonly used in the design and verification of digital circuits at the register-transfer level of abstraction. It is also used in the verification of analog circuits and mixed-signal circuits, as well as in the design of genetic circuits. In 2009, the Verilog standard was merged into the SystemVerilog standard, creating IEEE Standard 1800-2009. Since then, Verilog is officially part of the SystemVerilog language. The current version is IEEE standard 1800-2017.

### Network simulation software

More complex circuits are analyzed with circuit simulation software such as SPICE and EMTP.

SPICE is a general-purpose, open-source analog electronic circuit simulator. It is a program used in integrated circuit and board-level design to check the integrity of circuit designs and to predict circuit behavior.

#### Linearization around operating point

When faced with a new circuit, the software first tries to find a steady state solution wherein all the nodes conform to Kirchhoff's Current Law and the voltages across and through each element of the circuit conform to the voltage/current equations governing that element.

In systems theory, a system or a process is in a steady state if the variables which define the behavior of the system or the process are unchanging in time. In continuous time, this means that for those properties p of the system, the partial derivative with respect to time is zero and remains so:

Once the steady state solution is found, the software can analyze the response to perturbations using piecewise approximation, harmonic balance or other methods.

#### Piece-wise linear approximation

Software such as the PLECS interface to Simulink uses piecewise linear approximation of the equations governing the elements of a circuit. The circuit is treated as a completely linear network of ideal diodes. Every time a diode switches from on to off or vice versa, the configuration of the linear network changes. Adding more detail to the approximation of equations increases the accuracy of the simulation, but also increases its running time. PLECS is a software tool for system-level simulations of electrical circuits developed by Plexim. It is especially designed for power electronics but can be used for any electrical network. Simulink is a MATLAB-based graphical programming environment for modeling, simulating and analyzing multidomain dynamical systems. Its primary interface is a graphical block diagramming tool and a customizable set of block libraries. It offers tight integration with the rest of the MATLAB environment and can either drive MATLAB or be scripted from it. Simulink is widely used in automatic control and digital signal processing for multidomain simulation and model-based design.

In mathematics and statistics, a piecewise linear, PL or segmented function is a real-valued function defined on the real numbers or a segment thereof, whose graph is composed of straight-line sections. It is a piecewise-defined function, each of whose pieces is an affine function.

### Synthesis

Simple circuits may be designed by connecting a number of elements or functional blocks such as integrated circuits.

More complex digital circuits are typically designed with the aid of computer software. Logic circuits (and sometimes mixed mode circuits) are often described in such hardware description languages as HDL, VHDL or Verilog, then synthesized using a logic synthesis engine.

In computer engineering, a hardware description language (HDL) is a specialized computer language used to describe the structure and behavior of electronic circuits, and most commonly, digital logic circuits.

In electronics, logic synthesis is a process by which an abstract specification of desired circuit behavior, typically at register transfer level (RTL), is turned into a design implementation in terms of logic gates, typically by a computer program called a synthesis tool. Common examples of this process include synthesis of designs specified in hardware description languages, including VHDL and Verilog. Some synthesis tools generate bitstreams for programmable logic devices such as PALs or FPGAs, while others target the creation of ASICs. Logic synthesis is one aspect of electronic design automation.

## Related Research Articles An electrical network is an interconnection of electrical components or a model of such an interconnection, consisting of electrical elements. An electrical circuit is a network consisting of a closed loop, giving a return path for the current. Linear electrical networks, a special type consisting only of sources, linear lumped elements, and linear distributed elements, have the property that signals are linearly superimposable. They are thus more easily analyzed, using powerful frequency domain methods such as Laplace transforms, to determine DC response, AC response, and transient response.

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.

Electronic design automation (EDA), also referred to as electronic computer-aided design (ECAD), is a category of software tools for designing electronic systems such as integrated circuits and printed circuit boards. The tools work together in a design flow that chip designers use to design and analyze entire semiconductor chips. Since a modern semiconductor chip can have billions of components, EDA tools are essential for their design.

The IEEE 1164 standard is a technical standard published by the IEEE in 1993. It describes the definitions of logic values to be used in electronic design automation, for the VHDL hardware description language. It was sponsored by the Design Automation Standards Committee of the Institute of Electrical and Electronics Engineers (IEEE). The standardization effort was based on the donation of the Synopsys MVL-9 type declaration.

Small-signal modeling is a common analysis technique in electronics engineering which is used to approximate the behavior of electronic circuits containing nonlinear devices with linear equations. It is applicable to electronic circuits in which the AC signals, the time-varying currents and voltages in the circuit, have a small magnitude compared to the DC bias currents and voltages. A small-signal model is an AC equivalent circuit in which the nonlinear circuit elements are replaced by linear elements whose values are given by the first-order (linear) approximation of their characteristic curve near the bias point. Quite Universal Circuit Simulator (Qucs) is a free-software electronics circuit simulator software released under GPL. It gives you the ability to set up a circuit with a graphical user interface and simulate the large-signal, small-signal and noise behaviour of the circuit. Pure digital simulations are also supported using VHDL and/or Verilog.

Verilog-AMS is a derivative of the Verilog hardware description language that includes analog and mixed-signal extensions (AMS) in order to define the behavior of analog and mixed-signal systems. It extends the event-based simulator loops of Verilog/SystemVerilog/VHDL, by a continuous-time simulator, which solves the differential equations in analog-domain. Both domains are coupled: analog events can trigger digital actions and vice versa.

Verilog-A is an industry standard modeling language for analog circuits. It is the continuous-time subset of Verilog-AMS.

Flow to HDL tools and methods convert flow-based system design into a hardware description language (HDL) such as VHDL or Verilog. Typically this is a method of creating designs for field-programmable gate array, application-specific integrated circuit prototyping and digital signal processing (DSP) design. Flow-based system design is well-suited to field-programmable gate array design as it is easier to specify the innate parallelism of the architecture. Electronic circuit simulation uses mathematical models to replicate the behavior of an actual electronic device or circuit. Simulation software allows for modeling of circuit operation and is an invaluable analysis tool. Due to its highly accurate modeling capability, many colleges and universities use this type of software for the teaching of electronics technician and electronics engineering programs. Electronics simulation software engages the user by integrating him or her into the learning experience. These kinds of interactions actively engage learners to analyze, synthesize, organize, and evaluate content and result in learners constructing their own knowledge.

Aldec, Inc. is a privately owned electronic design automation company based in Henderson, Nevada that provides software and hardware used in creation and verification of digital designs targeting FPGA and ASIC technologies.

The Design Automation Standards Committee (DASC) is a subgroup of interested individuals members of the Institute of Electrical and Electronics Engineers (IEEE) Computer Society and Standards Association. It oversees IEEE Standards that are related to computer-aided design. It is part of the IEEE Computer Society.

VHDL-AMS is a derivative of the hardware description language VHDL. It includes analog and mixed-signal extensions (AMS) in order to define the behavior of analog and mixed-signal systems. The finite element method (FEM) is a numerical method for solving problems of engineering and mathematical physics. Typical problem areas of interest include structural analysis, heat transfer, fluid flow, mass transport, and electromagnetic potential. The analytical solution of these problems generally require the solution to boundary value problems for partial differential equations. The finite element method formulation of the problem results in a system of algebraic equations. The method approximates the unknown function over the domain. To solve the problem, it subdivides a large system into smaller, simpler parts that are called finite elements. The simple equations that model these finite elements are then assembled into a larger system of equations that models the entire problem. FEM then uses variational methods from the calculus of variations to approximate a solution by minimizing an associated error function. In electronics and chaos theory, Chua's diode is a type of two-terminal, nonlinear active resistor which can be described with piecewise-linear equations. It is an essential part of Chua's circuit, a simple electronic oscillator circuit which exhibits chaotic oscillations and is widely used as an example for a chaotic system. It is implemented as a voltage-controlled, nonlinear negative resistor.

The following outline is provided as an overview of and topical guide to electronics: