A digital system is a combination of devices designed to manipulate logical information or physical quantities that are represented in digital form; that is, the quantities can take on only discrete values.
These devices are most often electronic, but they can also be mechanical, magnetic, or pneumatic. Some of the more familiar digital systems include digital computers and calculators, digital audio and video equipment, and the telephone system—the world’s largest digital system.
Advantages of Digital Techniques
An increasing majority of applications in electronics, as well as in most other technologies, use digital techniques to perform operations that were once performed using analog methods.
The chief reasons for the shift to digital technology are:
- 1. Digital systems are generally easier to design. The circuits used in digital systems are switching circuits, where exact values of voltage or current are not important, only the range (HIGH or LOW) in which they fall.
- 2. Information storage is easy. This is accomplished by special devices and circuits that can latch onto digital information and hold it for as long as necessary, and mass storage techniques that can store billions of bits of
information in a relatively small physical space. Analog storage capabilities are, by contrast, extremely limited.
- 3. Accuracy and precision are easier to maintain throughout the system. Once a signal is digitized, the information it contains does not deteriorate as it is processed. In analog systems, the voltage and current signals tend to
be distorted by the effects of temperature, humidity, and component tolerance variations in the circuits that process the signal.
- 4. Operation can be programmed. It is fairly easy to design digital systems whose operation is controlled by a set of stored instructions called a program. Analog systems can also be programmed, but the variety and the complexity of the available operations are severely limited.
- 5. Digital circuits are less affected by noise. Spurious fluctuations in voltage (noise) are not as critical in digital systems because the exact value of a voltage is not important, as long as the noise is not large enough to prevent us from distinguishing a HIGH from a LOW.
- 6. More digital circuitry can be fabricated on IC chips. It is true that analog circuitry has also benefited from the tremendous development of IC technology, but its relative complexity and its use of devices that cannot be economically integrated (high-value capacitors, precision resistors, inductors, transformers) have prevented analog systems from achieving the same high degree of integration.