Page 161 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

142 H Chapter Thirfeen

The sampling usually occurs at regular time intervals and is triggered by the
digital part of the system. The complete range of values that the analog signal
can assume is divided into a set of discrete bands or quanta. At each sample
time, the A/D converter determines which band the analog signal falls into
(this is the “quantization” part of the process) and outputs the equivalent
binary code for that band.
The main factor governing the accuracy of the conversion is the number
of bands used. For example, a 3-bit code can represent only eight bands, each
encompassing 12.5% of the analog signal’s range, while a 12-bit code can
represent 4,096 bands, each encompassing 0.025% of the signal’s range.

Dig ital-to-Analog
A D/A converter accepts a digital code and transforms it into a correspond-
ing analog current or voltage suitable for use by means of an appropriate trans-
ducer called an actuator. For example, a loudspeaker is an actuator that converts
an electrical signal into sound. The digital-to-analog conversion process can be
represented as shown in Figure 13-4.

Digital-to- Analog
n Signal Processing - Actuator
(Conditioning)

Digital Domain Analog Domain
b4

Figure 1 3-4. Digital-to-analog conversion process

The conversions usually occur at regular time intervals and are triggered
by a clock signal from the digital part of the system. The output from the D/A
converter typically undergoes some form of conditioning before being passed to
the actuator. For example, in the case of an audio system, the “staircase-like”
signal coming out of the D/A converter will be “smoothed” before being passed
to an amplifier (not shown in Figure 13-4) and, ultimately, to the loudspeaker.