A/D converter

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A/D converter (ADC) Short for analog-to-digital converter. A device that can accept an analog, i.e. continuous, signal whose amplitude lies within a given range, and produce an equivalent digital signal, i.e. an n-bit parallel binary word that represents this analog signal. The analog signal is “examined” at discrete fixed intervals of time by means of a sampling process in order to produce the digital signal. Analog signals originating from devices such as analog sensors or tachogenerators may thus be converted into a form that can then be processed by, say, a microprocessor.

The resolution of an A/D converter gives the smallest change in analog input that can be discriminated by the device. If the resolution of an n-bit A/D converter is ΔV, then its range is either 0 to ΔV(2n – 1)

or ±ΔV(2n–1 – 1)

according as it is unsigned or signed. In practice, the value of n is usually 8, 10, 12, 14, or 16. Since the resolution is finite, the conversion process introduces quantization noise (see discrete and continuous systems). A/D converters are available in integrated circuit form. See also D/A converter.

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