## Difference Between Analog and Digital Signals

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A digital signal is a signal that is being used to represent data as a sequence of discrete values; at any given time it can only take on one of a finite number of values. Simple digital signals represent information in discrete bands of analog levels. All levels within a band of values represent the same information state.

In most digital circuitsthe signal can have two possible values; this is called a binary signal or logic signal. These correspond to the two values "zero" and "one" or "false" and "true" of the Boolean domainso at any given time a binary signal represents one binary digit bit.

Because of this discretizationrelatively small changes to the analog signal levels do not leave the discrete envelope, and as a result are what is the difference between an analog and a binary input signal by signal state sensing circuitry.

As a result, digital signals have noise immunity ; electronic noiseprovided it is not too great, will not affect digital circuits, whereas noise always degrades the operation of analog signals to some degree. Digital signals having more than two states are occasionally used; circuitry using such signals is called multivalued logic. For example, signals that can assume three what is the difference between an analog and a binary input signal states are called three-valued logic.

In a digital signal, the physical quantity representing the information may be a variable electric current or voltage, the intensity, phase or polarization of an optical or other electromagnetic fieldacoustic pressure, the magnetization of a magnetic storage media, etcetera. Digital signals are used in all digital electronicsnotably computing equipment and data transmission.

In digital electronics a digital signal is a pulse train a pulse amplitude modulated signali. In digital signal processinga digital signal is a representation of a physical signal that is a sampled and quantized. A digital signal is an abstraction which is discrete in time and amplitude.

The signal's value only exists at regular time intervals, since only the values of the corresponding physical signal at those sampled moments are significant for further digital processing.

The digital signal is a sequence of codes drawn from a finite set of values. In digital communicationsa digital signal is a continuous-time physical signal, alternating between a discrete number of waveforms, [3] representing a bit stream message. The shape of the waveform depends what is the difference between an analog and a binary input signal transmission scheme, which may be either:.

In communications, sources of interference are usually present, and noise is frequently a significant problem. The effects of interference are typically minimized by filtering off interfering signals as much as possible and by using data redundancy.

The main advantages of digital signals for communications are often considered to be the immunity to noise that it may be possible to provide, and the ability, in many cases such as with audio and video data, to use data compression to greatly decrease the bandwidth that is required on the communication media.

In computer architecture and other digital systems, a waveform that switches between two voltage levels or less commonly, other waveforms representing the two states of a Boolean value 0 and 1, or Low and High, or false and true is referred to as a digital signal or logic signal or binary signal when it is interpreted in terms of only two possible digits. The clock signal is a special digital signal that is used to synchronize many digital circuits.

The image shown can be considered the waveform of a clock signal. Logic changes are triggered either by the rising edge or the falling edge. The given diagram is an example of the practical pulse and therefore we have introduced two new terms that are:. Although in a highly simplified and idealized model of a what is the difference between an analog and a binary input signal circuit we may wish for these transitions to occur instantaneously, no real world circuit is purely resistive and therefore no circuit can instantly change voltage levels.

This means that during a short, finite transition time the output may not properly reflect the input, and will not correspond to either a logically high or low voltage. The two states of a wire are usually represented by some measurement of an electrical property: Voltage is the most common, but current is used in some logic families.

A threshold is designed for each logic family. When below that threshold, the signal is lowwhen above high. To create a digital signal, an analog signal must be modulated with a control signal to produce it. As we have already seen, the simplest modulation, a type of unipolar line coding is simply to switch on and off a DC signal, so that high voltages are a '1' and low voltages are '0'. In digital radio schemes one or more carrier waves are amplitude or frequency or phase modulated with a signal to produce a digital signal suitable for transmission.

In Asymmetric Digital Subscriber Line over telephone wiresADSL does not primarily use binary logic; the digital signals for individual carriers are modulated with different valued logics, depending on the Shannon capacity of the individual channel.

Often digital signals are "sampled" by a clock signal at regular intervals by passing the signal through an "edge sensitive" flip-flop. When this is done the input is measured at those points in time, and the signal from that time is passed through to the output and the output is then held steady till the next clock.

This process is the basis of synchronous logicand the system is also used in digital signal processing. However, asynchronous logic also exists, which uses no what is the difference between an analog and a binary input signal clock, and generally operates more quickly, and may use less power, but is significantly harder to design.

Digital signal signal processing. A logic signal waveform: The Art Of Electronics, 2nd Ed. A digital signal is a special form of discrete-time signal which is discrete in both time and amplitude, obtained by permitting each value sample of a discrete-time signal to acquire a finite set of values quantizationassigning it a numerical symbol according to a code A digital signal is a sequence or list of numbers drawn from a finite set.

Chitode, Communication Systems Digital signal electronics Boolean algebra Logic synthesis Logic in computer science Computer architecture Digital signal signal processing Digital signal processing What is the difference between an analog and a binary input signal minimization Switching circuit theory. Logic synthesis Register-transfer level Formal equivalence checking Synchronous logic Asynchronous logic Finite-state machine. Computer hardware Digital audio radio Digital photography Digital telephone Digital video cinema television Electronic literature.

Line coding digital baseband transmission. Unipolar encoding Bipolar encoding On-off keying. Carrier-suppressed return-to-zero Alternate-phase return-to-zero. Coaxial cable Fiber-optic communication Optical fiber Free-space optical communication Molecular communication Radio waves Transmission line.

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There is a significant distinction between an analog system and a digital system , in the same way that there is a significant difference between analog and digital data. This book is going to consider both analog and digital topics, so it is worth taking some time to discuss the differences, and to display the different notations that will be used with each. A system is a continuous-time system if it takes a continuous-time input signal, and outputs a continuous-time output signal.

Here is an example of an analog waveform:. A signal is called discrete-time if it is only defined for particular points in time. A discrete-time system takes discrete-time input signals, and produces discrete-time output signals. The following image shows the difference between an analog waveform and the sampled discrete time equivalent: A signal is called Quantized if it can only be certain values, and cannot be other values.

This concept is best illustrated with examples:. The last example concerning computers is the most relevant, because quantized systems are frequently computer-based.

Systems that are implemented with computer software and hardware will typically be quantized. Here is an example waveform of a quantized signal. Notice how the magnitude of the wave can only take certain values, and that creates a step-like appearance. This image is discrete in magnitude, but is continuous in time:.

An analog system is a system that represents data using a direct conversion from one form to another. In other words, an analog system is a system that is continuous in both time and magnitude. If we have a given motor, we can show that the output of the motor rotation in units of radians per second, for instance is a function of the voltage that is input to the motor.

We can show the relationship as such:. For any value of v we can calculate out specifically what the rotational speed of the motor should be. Consider a standard analog clock, which represents the passage of time though the angular position of the clock hands.

We can denote the angular position of the hands of the clock with the system of equations:. The positions of all the different hands of the clock are dependent on functions of time. Digital data always have a certain granularity, and therefore there will almost always be an error associated with using such data, especially if we want to account for all real numbers. The tradeoff, of course, to using a digital system is that our powerful computers with our powerful, Moore's law microprocessor units, can be instructed to operate on digital data only.

This benefit more than makes up for the shortcomings of a digital representation system. Discrete systems will be denoted inside square brackets, as is a common notation in texts that deal with discrete values. For instance, we can denote a discrete data set of ascending numbers, starting at 1, with the following notation:. Analog, or "non-discrete" values are denoted in regular expression syntax, using parenthesis. Here is an example of an analog waveform and the digital equivalent.

Notice that the digital waveform is discrete in both time and magnitude:. As a common example, let's consider a digital clock: The digital clock represents time with binary electrical data signals of 1 and 0. The 1's are usually represented by a positive voltage, and a 0 is generally represented by zero voltage.

Counting in binary, we can show that any given time can be represented by a base-2 numbering system:. But what happens if we want to display a fraction of a minute, or a fraction of a second? A typical digital clock has a certain amount of precision , and it cannot express fractional values smaller than that precision.

Hybrid Systems are systems that have both analog and digital components. Devices called samplers are used to convert analog signals into digital signals, and Devices called reconstructors are used to convert digital signals into analog signals.

Because of the use of samplers, hybrid systems are frequently called sampled-data systems. Most modern automobiles today have integrated computer systems that monitor certain aspects of the car, and actually help to control the performance of the car. The speed of the car, and the rotational speed of the transmission are analog values, but a sampler converts them into digital values so the car computer can monitor them.

The digital computer will then output control signals to other parts of the car, to alter analog systems such as the engine timing, the suspension, the brakes, and other parts.

Because the car has both digital and analog components, it is a hybrid system. A system is considered continuous-time if the signal exists for all time.

Frequently, the terms "analog" and "continuous" will be used interchangeably, although they are not strictly the same. Discrete magnitude systems are systems where the signal value can only have certain values. Discrete time systems are systems where signals are only available or valid at particular times.

Computer systems are discrete in the sense of 3 , in that data is only read at specific discrete time intervals, and the data can have only a limited number of discrete values. A discrete-time system has a sampling time value associated with it, such that each discrete value occurs at multiples of the given sampling time. We will denote the sampling time of a system as T. We can equate the square-brackets notation of a system with the continuous definition of the system as follows:.

Notice that the two notations show the same thing, but the first one is typically easier to write, and it shows that the system in question is a discrete system. This book will use the square brackets to denote discrete systems by the sample number n, and parenthesis to denote continuous time functions. The process of converting analog information into digital data is called "Sampling". The process of converting digital data into an analog signal is called "Reconstruction".

We will talk about both processes in a later chapter. For more information on the topic than is available in this book, see the Analog and Digital Conversion wikibook. Here is an example of a reconstructed waveform. Notice that the reconstructed waveform here is quantized because it is constructed from a digital signal:. From Wikibooks, open books for an open world. Analog A signal is considered analog if it is defined for all points in time and if it can take any real magnitude value within its range.

We can show the relationship as such: We can denote the angular position of the hands of the clock with the system of equations: Different positions on a clock face correspond directly to different times of the day. Digital A signal or system is considered digital if it is both discrete-time and quantized. Counting in binary, we can show that any given time can be represented by a base-2 numbering system: We are not using the word "continuous" here in the sense of continuously differentiable , as is common in math texts.