Digital circuit

A digital circuit is based on a number of discrete voltage levels, as distinct from an
analog circuit that uses continuous voltages to represent variables directly. Digital circuits
are the most common mechanical representation of Boolean algebra and are the basis of
all digital computers. They can also be used to process digital information without being
connected up as a computer.

Such circuits are referred to as “random logic”.In most cases the number of states is two, and these states are represented by two voltage levels: one near to zero volts and one at a higher level depending on the supply voltage in use. These two levels are often represented as “Low” and “High.” To most electronic engineers, the terms “digital circuit”, “digital system” and “logic” are
interchangeable in the context of digital circuits.

Digital circuits are less affected by noise. In fact, if the noise is below a certain
level (the noise margin), a digital circuit behaves as if there was no noise at all —
this is a necessary and sufficient property for a circuit to be considered a digital
circuit. However, if the noise exceeds this level, the digital circuit can give
catastrophically wrong results. Theoretically, there is no data-loss when copying digital data. This is a great advantage over analog systems, which faithfully reproduce every bit of noise that
makes its way into the signal.


Digital signals can thus be regenerated to achieve lossless data transmission,
within certain limits. Analog signal transmission and processing, by contrast,
always introduces noise. Digital systems interface well with computers and are easy to control with software. It is often possible to add new features to a digital system without
changing hardware, and to do this remotely, just by uploading new software. Design errors or bugs can be worked-around with a software upgrade, after the product is in customer hands.