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 ?
Protecting source programming from illicit copying and piracy during analog to digital conversion is a key factor driving the growth of the digital video broadcast and personal video recording (PVR) markets," said Michael Malloy, product marketing manager for Philips Semiconductors.
All of the decoders are fully certified to detect Macrovision's Copy Protection signals to ensure that copyrighted source programs remain copy-protected throughout the entire analog to digital conversion process.
The AD8351 simplifies analog to digital conversion by allowing the user to adjust the common mode voltage and set the gain from 0 dB to 26 dB (voltage gains from 1 to 20) through a single external resistor.
The result is a combination of video decoders and synchronizers that produce unmatched analog to digital conversion quality and an audio synchronizer with 24 bit A/D and D/A that works with the video synchronizers for lip sync.

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