Digital electronics
In an 1886 letter, Charles Sanders Peirce described how logical operations could be carried out by electrical switching circuits.
Walther Bothe, inventor of the coincidence circuit, shared the 1954 Nobel Prize in physics, for creating the first modern electronic AND gate in 1924.
In World War II, mechanical analog computers were used for specialized military applications such as calculating torpedo aiming.
[3] Claude Shannon, demonstrating that electrical applications of Boolean algebra could construct any logical numerical relationship, ultimately laid the foundations of digital computing and digital circuits in his master's thesis of 1937, which is considered to be arguably the most important master's thesis ever written, winning the 1939 Alfred Noble Prize.
[7][8] 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 vacuum tubes.
Spitzer studied the mechanism of thermally grown oxides, fabricated a high quality Si/SiO2 stack and published their results in 1960.
[30] Along with MOS large-scale integration (LSI), these factors make the MOSFET an important switching device for digital circuits.
[44] For example, a continuous audio signal transmitted as a sequence of 1s and 0s, can be reconstructed without error, provided the noise picked up in transmission is not enough to prevent identification of the 1s and 0s.
In an analog system, additional resolution requires fundamental improvements in the linearity and noise characteristics of each step of the signal chain.
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.
For example, battery-powered cellular phones often use a low-power analog front-end to amplify and tune the radio signals from the base station.
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.
For example, a single-bit error in audio data stored directly as linear pulse-code modulation causes, at worst, a single audible click.
But when using audio compression to save storage space and transmission time, a single bit error may cause a much larger disruption.
A logic gate is generally created from one or more electrically controlled switches, usually transistors but thermionic valves have seen historic use.
Another form of digital circuit is constructed from lookup tables, (many sold as "programmable logic devices", though other kinds of PLDs exist).
Lookup tables can perform the same functions as machines based on logic gates, but can be easily reprogrammed without changing the wiring.
Integrated circuits consist of multiple transistors on one silicon chip and are the least expensive way to make a large number of interconnected logic gates.
Logic redundancy can be removed by several well-known techniques, such as binary decision diagrams, Boolean algebra, Karnaugh maps, the Quine–McCluskey algorithm, and the heuristic computer method.
Synchronous sequential systems are made using flip flops that store inputted voltages as a bit only when the clock changes.
These are usually designed using synchronous register transfer logic and written with hardware description languages such as VHDL or Verilog.
Tool flows for large logic systems such as microprocessors can be thousands of commands long, and combine the work of hundreds of engineers.
Writing and debugging tool flows is an established engineering specialty in companies that produce digital designs.
Serial scans have only one or two wires to carry the data, and minimize the physical size and expense of the infrequently used test logic.
Sometimes this results in more complicated designs with respect to the underlying digital logic but nevertheless reduces the number of components, board size, and even power consumption.
Even so, many of these machines had complex, well-rehearsed repair procedures, and would be nonfunctional for hours because a tube burned-out, or a moth got stuck in a relay.
The switching speed describes how long it takes a logic output to change from true to false or vice versa.
In 2009, researchers discovered that memristors can implement a Boolean state storage and provides a complete logic family with very small amounts of space and power, using familiar CMOS semiconductor processes.
[52] The discovery of superconductivity has enabled the development of rapid single flux quantum (RSFQ) circuit technology, which uses Josephson junctions instead of transistors.
