A DAC converts an abstract finite-precision number (usually a fixed-point binary number) into a concrete physical quantity (e.g., a voltage or a pressure).

**Digital To
Analog Conversion**

A
DAC converts an abstract finite-precision number (usually a fixed-point binary
number) into a concrete physical quantity (e.g., a voltage or a pressure). In
particular, DACs are often used to convert finite-precision time series data to
a continually-varying physical signal.

A
typical DAC converts the abstract numbers into a concrete sequence of impulses
that are then processed by a reconstruction filter using some form of
interpolation to fill in data between the impulses.

Other
DAC methods (e.g., methods based on Delta-sigma modulation) produce a
pulse-density modulated signal that can then be filtered in a similar way to
produce a smoothly-varying signal.By the Nyquist–Shannon sampling theorem,
sampled data can be reconstructed perfectly provided that its bandwidth meets certain
requirements (e.g., a baseband signal with bandwidth less than the Nyquist
frequency). However, even with an ideal reconstruction filter, digital sampling
introduces quantization that makes perfect reconstruction practically
impossible. Increasing the digital resolution (i.e., increasing the number of
bits used in each sample) or introducing sampling dither can reduce this error.

DACs
are at the beginning of the analog signal chain, which makes them very
important to system performance. The most important characteristics of these
devices are:

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