Digital electronics - Wikipedia, the free encyclopedia. Digital electronics. A digital signal has two or more distinguishable waveforms, in this example, high voltage and low voltages, each of which can be mapped onto a digit. An industrial digital controller.
Digital electronics or digital (electronic) circuits are electronics that handle digital signals . All levels within a band of values represent the same information state. Because of this discretization, relatively small changes to the analog signal levels due to manufacturing tolerance, signal attenuation or noise do not leave the discrete envelope, and as a result are ignored by signal state sensing circuitry. In most cases, the number of these states is two, and they are represented by two voltage bands: one near a reference value (typically termed as . These correspond to the false and true values of the Boolean domain respectively. Digital techniques are useful because it is easier to get an electronic device to switch into one of a number of known states than to accurately reproduce a continuous range of values.
Digital electronic circuits are usually made from large assemblies of logic gates, simple electronic representations of Boolean logic functions. Digital logic as we know it was the brain- child of George Boole, in the mid 1. Boole died young, but his ideas lived on. In an 1. 88. 6 letter, Charles Sanders Peirce described how logical operations could be carried out by electrical switching circuits.
Lee De Forest's modification, in 1. Fleming valve can be used as an AND logic gate. Ludwig Wittgenstein introduced a version of the 1. Tractatus Logico- Philosophicus (1. Walther Bothe, inventor of the coincidence circuit, got part of the 1.
Digital Electronics Questions and Answers. Digital Electronics Interview Questions and Answers. Here you can find Digital Electronics interview questions with answers and explanation. Why Digital Electronics?
- Advanced Digital Electronics Interview Questions Answers. This is committed to provide the most applicable as well as related pdf within our data bank on. Download full version PDF for Advanced Digital Electronics.
- Digital Electronics Multiple Choice Questions. This is committed to provide the most applicable as well as related pdf within our data bank on. Download full version PDF for Digital Electronics Multiple Choice.
Nobel Prize in physics, for the first modern electronic AND gate in 1. Mechanicalanalog computers started appearing in the first century and were later used in the medieval era for astronomical calculations.
In World War II, mechanical analog computers were used for specialized military applications such as calculating torpedo aiming. During this time the first electronic digital computers were developed. Originally they were the size of a large room, consuming as much power as several hundred modern personal computers (PCs).
It was the world's first working programmable, fully automatic digital computer. The bipolar junction transistor was invented in 1.
From 1. 95. 5 onwards transistors replaced vacuum tubes in computer designs, giving rise to the . Silicon junction transistors were much more reliable than vacuum tubes and had longer, indefinite, service life. Transistorized computers could contain tens of thousands of binary logic circuits in a relatively compact space. At the University of Manchester, a team under the leadership of Tom Kilburn designed and built a machine using the newly developed transistors instead of valves. Manufacturing yields were also quite low by today's standards.
Digital Logic multiple choice questions answer for various academic and competitive exams. IES, Bank exams or any other such exam. Digital Electronics Mcq; Digital Logic Mcq Pdf Download. Questions and answers on digital electronics output. Frequently asked very important interview and Viva questions on digital electronics with proper answers. 8 Responses to Interview & Viva questions and answers on Digital. The Digital Electronics Basics series present the fundamental theories and concepts taught at entry level electronics courses at both 2 year and 4 year institutions. This series of content provides examples to professors to.
As the technology progressed, millions, then billions. An hour of music can be stored on a compact disc using about 6 billion binary digits. In a digital system, a more precise representation of a signal can be obtained by using more binary digits to represent it. While this requires more digital circuits to process the signals, each digit is handled by the same kind of hardware, resulting in an easily scalable system. In an analog system, additional resolution requires fundamental improvements in the linearity and noise characteristics of each step of the signal chain. Computer- controlled digital systems can be controlled by software, allowing new functions to be added without changing hardware.
Often this can be done outside of the factory by updating the product's software. So, the product's design errors can be corrected after the product is in a customer's hands.
Information storage can be easier in digital systems than in analog ones. The noise- immunity of digital systems permits data to be stored and retrieved without degradation. In an analog system, noise from aging and wear degrade the information stored. In a digital system, as long as the total noise is below a certain level, the information can be recovered perfectly. Even when more significant noise is present, the use of redundancy permits the recovery of the original data provided too many errors do not occur. In some cases, digital circuits use more energy than analog circuits to accomplish the same tasks, thus producing more heat which increases the complexity of the circuits such as the inclusion of heat sinks.
In portable or battery- powered systems this can limit use of digital systems. For example, battery- powered cellular telephones often use a low- power analog front- end to amplify and tune in the radio signals from the base station. However, a base station has grid power and can use power- hungry, but very flexible software radios. Such base stations can be easily reprogrammed to process the signals used in new cellular standards. Digital circuits are sometimes more expensive, especially in small quantities.
Most useful digital systems must translate from continuous analog signals to discrete digital signals. This causes quantization errors. Quantization error can be reduced if the system stores enough digital data to represent the signal to the desired degree of fidelity. The Nyquist- Shannon sampling theorem provides an important guideline as to how much digital data is needed to accurately portray a given analog signal. In some systems, if a single piece of digital data is lost or misinterpreted, the meaning of large blocks of related data can completely change.
Because of the cliff effect, it can be difficult for users to tell if a particular system is right on the edge of failure, or if it can tolerate much more noise before failing. Digital fragility can be reduced by designing a digital system for robustness. For example, a parity bit or other error management method can be inserted into the signal path. These schemes help the system detect errors, and then either correct the errors, or at least ask for a new copy of the data. In a state- machine, the state transition logic can be designed to catch unused states and trigger a reset sequence or other error recovery routine. Digital memory and transmission systems can use techniques such as error detection and correction to use additional data to correct any errors in transmission and storage. On the other hand, some techniques used in digital systems make those systems more vulnerable to single- bit errors.
These techniques are acceptable when the underlying bits are reliable enough that such errors are highly unlikely. A single- bit error in audio data stored directly as linear pulse code modulation (such as on a CD- ROM) causes, at worst, a single click. Instead, many people use audio compression to save storage space and download time, even though a single- bit error may corrupt the entire song. Construction. Each logic gate is designed to perform a function of boolean logic when acting on logic signals. A logic gate is generally created from one or more electrically controlled switches, usually transistors but thermionic valves have seen historic use. The output of a logic gate can, in turn, control or feed into more logic gates. Integrated circuits consist of multiple transistors on one silicon chip, and are the least expensive way to make large number of interconnected logic gates.
Integrated circuits are usually designed by engineers using electronic design automation software (see below for more information) to perform some type of function. Integrated circuits are usually interconnected on a printed circuit board which is a board which holds electrical components, and connects them together with copper traces. Each logic symbol is represented by a different shape. The actual set of shapes was introduced in 1. IEEE/ANSI standard 9. Lookup tables can perform the same functions as machines based on logic gates, but can be easily reprogrammed without changing the wiring. This means that a designer can often repair design errors without changing the arrangement of wires.
Therefore, in small volume products, programmable logic devices are often the preferred solution. They are usually designed by engineers using electronic design automation software. When the volumes are medium to large, and the logic can be slow, or involves complex algorithms or sequences, often a small microcontroller is programmed to make an embedded system.
These are usually programmed by software engineers. When only one digital circuit is needed, and its design is totally customized, as for a factory production line controller, the conventional solution is a programmable logic controller, or PLC.
These are usually programmed by electricians, using ladder logic. Structure of digital systems.
When the complexity is less, the circuit also has fewer errors and less electronics, and is therefore less expensive. The most widely used simplification is a minimization algorithm like the Espresso heuristic logic minimizer within a CAD system, although historically, binary decision diagrams, an automated Quine. Some analysis methods only work with particular representations.
The classical way to represent a digital circuit is with an equivalent set of logic gates. Another way, often with the least electronics, is to construct an equivalent system of electronic switches (usually transistors). One of the easiest ways is to simply have a memory containing a truth table.
The inputs are fed into the address of the memory, and the data outputs of the memory become the outputs. For automated analysis, these representations have digital file formats that can be processed by computer programs.
Most digital engineers are very careful to select computer programs (. Most digital systems divide into . It is basically a representation of a set of logic functions, as already discussed. A sequential system is a combinational system with some of the outputs fed back as inputs. This makes the digital machine perform a .