analog-to-digital converter

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analog-to-digital converter

[¦an·əl‚äg tə ¦dij·ət·əl kən′vərd·ər]
A device which translates continuous analog signals into proportional discrete digital signals.

Analog-to-digital converter

A device for converting the information contained in the value or magnitude of some characteristic of an input signal, compared to a standard or reference, to information in the form of discrete states of a signal, usually with numerical values assigned to the various combinations of discrete states of the signal.

Analog-to-digital (A/D) converters are used to transform analog information, such as audio signals or measurements of physical variables (for example, temperature, force, or shaft rotation) into a form suitable for digital handling, which might involve any of these operations: (1) processing by a computer or by logic circuits, including arithmetical operations, comparison, sorting, ordering, and code conversion, (2) storage until ready for further handling, (3) display in numerical or graphical form, and (4) transmission.

If a wide-range analog signal can be converted, with adequate frequency, to an appropriate number of two-level digits,or bits, the digital representation of the signal can be transmitted through a noisy medium without relative degradation of the fine structure of the original signal. See Computer graphics, Data communications, Digital computer

Conversion involves quantizing and encoding. Quantizing means partitioning the analog signal range into a number of discrete quanta and determining to which quantum the input signal belongs. Encoding means assigning a unique digital code to each quantum and determining the code that corresponds to the input signal. The most common system is binary, in which there are 2n quanta (where n is some whole number), numbered consecutively; the code is a set of n physical two-valued levels or bits (1 or 0) corresponding to the binary number associated with the signal quantum.

The illustration shows a typical three-bit binary representation of a range of input signals, partitioned into eight quanta. For example, a signal in the vicinity of 3/8; full scale (between 5/16 and 7/16) will be coded 011 (binary 3).

A three-bit binary representation of a range of input signalsenlarge picture
A three-bit binary representation of a range of input signals
References in periodicals archive ?
This PC/104-compliant card includes a 16 channel, 12-bit analog-to-digital (A/D) converter, 8 channel, 12-bit digital-to-analog (D/A) converter, and 48 lines of digital I/O.
NYSE: ADI), a global leader in high performance semiconductors for signal processing applications and the market leader in data conversion technology, is introducing a family of high-speed 10- and 12-bit analog-to-digital converters (ADCs) targeted for broadband communications and wireless infrastructure applications--such as cable modem termination systems, third and fourth generation microcell and picocell base stations, and fixed point-to-point radios--where low power consumption is required to accommodate smaller form factors, but high-quality conversion performance cannot be sacrificed.