Digital electronics

Digital technology is concerned with the processing of value-and discrete-time values and number sequences, referred to as digital signals. Typical components are logic gates, microprocessors and data storage, but no amplifier as in the analog technology.

The signals of both technologies can be transformed into so-called mixed-signal integrated circuits, for example, in analog - to-digital converters and digital - to-analog converters each other.

Construction

Digital technology works in contrast to the analog technology with discrete rather than continuous signals. In addition, the signals usually have only a small range of values , usually of two values in the form of the dual system. These values are usually 1 and 0 or H and L, which represent the Boolean constants "true" and " false ". If a high level with 1 and a low level is represented by 0, is called positive logic, where a reversed situation of negative logic. Furthermore, there are digital circuits with more than two value states, such as MLC memory cells to represent more than one bit of information per MLC memory cell can.

In addition, other possible states must be observed in the real digital circuits yet. These resources include the indefinite and the high-impedance state.

Digital circuits consist mainly of logic elements such as AND, NAND, OR, NOR, NOT, XOR, XNOR and others with whom digital yes / no information is linked together, for example in the context of counters or flip-flops. More complex applications processors. In theory suffices to choose one type (NAND or NOR) of gates, then the "base " refers to reassemble all other logical functions. In digital technology, the dual system is used as a basis (as the above yes / no distinction ) usually using the Boolean algebra. So can be used for each logic element, a switching function create that describes how it works. In practice, one usually uses only NAND gates, which can be used to replicate the functions of the other gate.

Digital circuits, in addition to logical functions include time-dependent components, and further cycles or state-controlled (synchronous / asynchronous) work. Contains a digital circuit only logic elements without feedback from outputs to inputs, so it is called a switching network. Memory be used in addition, or to at least one output coupled to an input, there is a switching device or a vending machine. A microcontroller or processor consists mainly of logic elements, and is extended via a data bus with memory and other digital components. A staggered implementation of logic functions is possible. These can be hardwired or programmed.

Logic gate - Overview

Truth table

In order to achieve a logical 1 at the output y, so both inputs must be at logic 1.

Truth table

In order to achieve a logical 1 at the output y, so a logic 1 on both inputs, or need to be.

Truth table

In order to achieve a logical 1 at the output y, exactly one of the inputs must be set to logic 1.

Truth table

Thus, the output y is the complement of the input x.

A NAND gate is an AND gate with downstream NOT gate. Accordingly, it is an OR gate with downstream NOT gate, a NOR gate and an XOR gate with a subsequent non- gate an XNOR gate. With NAND or NOR gates can be reproduced by appropriate wiring all other logic gates.

Advantages of digital systems

Uniqueness; when comparing two numbers can be always uniquely identify the larger or determine equality
No creeping error propagation, thus very complex systems can be realized, and the loss-free transmission of signals over long distances is possible
Easily described by Boolean algebra and thus to construct
Easy to test

Advantages of digital signal processing over analog technology are, in addition to the lower cost of the components due to high integration density and simplified development, especially in the higher flexibility. Using special signal processors or computer circuits can be implemented in software. This functions can be quickly adapted to changing requirements. In addition, complex algorithms are easy to use, which would be analogous only with extremely high effort or not feasible.

Special developer tools (CAE ) and description languages such as VHDL or Verilog assist engineers with the rapid development of new applications and circuits.

Disadvantages of digital systems

The number of required circuit components is many times higher than in analog systems. However, this is compensated for by a high level of integration on the corresponding chip.
Loss of information. Due to quantization error in the conversion of analog to digital information

Applications

The genetic material is discretely encoded.
The human speech and writing consists of discrete symbols of a limited character set.
Money is discrete, it is not gold outweighed.
We measure the time (even on analog clocks ) with multiple discrete sites (English Digits ): hours, minutes, seconds - and thus digitally, although the time runs itself continuous ( analog).
Phones transmit telephone numbers in a discrete manner. Telegraph work discreetly during the connection.
Radio links worked historically first discreet and long was used for training a radio operator.

Digital electronics

Construction

Logic gate - Overview

Advantages of digital systems

Disadvantages of digital systems

Applications

Further Reading