Electronics

Digital electronics are the electronics that transformed our lives beginning in the 1970s. The personal computer is one of the best examples of this transformation because it has simplified tasks that were difficult or impossible for individuals to accomplish. Digital devices use simple "true-false" or "on-off" statements to represent information and to make decisions. In contrast, analog devices use a continuous system of values. Because digital devices only recognize one of two permissible signals, they are more tolerant to noise (unwanted electronic signals) and a range of components than analog devices. Digital systems are built of a collection of components that process, store, and transmit or communicate information. The basis of these components is the logic circuit that makes the true-false decision from what may be many true-false signals. The logic circuit is an integrated circuit from any one of a number of families of digital logic devices that use switches, transducers, and timing circuits to function. Digital logic gates are the most elementary inputs and outputs in a logic device. A logic gate is based on a simple operation in Boolean algebra (a form of mathematics that uses logic variables to express thought processes). For example, a logic gate may perform an "or," "and," or "not" function; to make it capable of a "nor" function, an "or" gate is followed by an inverter. By linking combinations of these gates, any decision is possible.

The most popular form of logic circuit is probably the transistor-transistor logic (TTL) circuit. High-speed systems use emitter coupled logic (ELC), and the complementary metal oxide semiconductor (CMOS) logic uses lower speeds to also lower power levels. Logic gates are also combined to make static-memory cells. These are combined in a rectangular array to form the random-access memory (RAM) familiar to home computer users. The binary digits that make up this memory are called "bits," and typical large-scale integrated (LSI) circuit memory chips have over 16,000 bits of static memory. Dynamic memory cells use capacitors to send memory to a selected cell or to "write" to that cell. Very-large-scale chips with 256,000 bits per chip were made beginning in the 1980s, and dynamic memory made these possible because of its high density.

Microprocessors have replaced combinations of switching and timing circuits. They are programmed to perform sets of tasks and a wider variety of logic functions. Electronic games and digital watches are examples of microprocessor systems. Digital methods have revolutionized music, library storage, medical electronics, and high definition television, among thousands of other tools that influence our lives daily. Future changes to socalled "computer architecture" are directed at greater speed; ultra-high-speed computers may operate by using superconducting circuits that operate at extremely cold temperatures, and integrated circuits that house hundreds of thousands of electronic components on one chip may be commonplace on our desktops.