 - Digital-to-analog conversion is a
process in which signals having a few (usually two) defined
levels or states (digital)
are converted into signals having a theoretically infinite number
of states (analog).
A common example is the processing, by a modem,of computer data
into audio-frequency (AF) tones that can be transmitted over a
twisted pair telephone line. The circuit that performs this function is a digital-to-analog converter (DAC).
Basically, digital-to-analog conversion is the
opposite of analog-to-digital conversion. In most cases, if an analog-to-digital
converter (ADC) is placed in a communications circuit after
a DAC, the digital signal output is identical to the digital
signal input. Also, in most instances when a DAC is placed after
an ADC, the analog signal output is identical to the analog
signal input.
Binary digital impulses, all by themselves,
appear as long strings of ones and zeros, and have no apparent
meaning to a human observer. But when a DAC is used to decode the
binary digital signals, meaningful output appears. This might be
a voice, a picture, a musical tune, or mechanical motion.
Both the DAC and the ADC are of significance in
some applications of digital signal processing. The intelligibility or fidelity
of an analog signal can often be improved by converting the
analog input to digital form using an ADC, then clarifying the
digital signal, and finally converting the "cleaned-up"
digital impulses back to analog form using an DAC.
| LAST UPDATED: |
11 Oct 2001
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