Digital systems
Introduction

Application of digital data processing systems is facilitated by greatly developed computer technology, especially by use of microprocessors, microcontrollers, microprocessor based personal computers and other programmable systems, especially programmable logic controllers (PLC). In practice, the digital systems have almost completely superseded their analogue counterparts, realized either by passive or active (e.g. operational amplifier) component circuits.

Equivalents of all analogue systems (e.g. controllers, filters, models) can be realized by digital systems. In addition, there is a kind of behavior, found in digital systems, which is unavailable to analogue systems: finite impulse response (FIR) systems, which do not have their equivalent in analogue domain. There are also other functions, inconvenient in analogue implementation (principally impossible or too complicated), e.g. nonlinear filters, statistical operations, identification or optimization tasks.

Digital systems are applied in numerous fields for many different functions. However, their structure and implementation are always very similar. The difference is in the design methodology and structural and parametric requirements. For example, the requirements for controller are stability and desired control performance. On the other hand, requirement for digital model is a maximum match in behavior to the original.