- Analogue electronics
Analogue electronics (or analog in
American English) are those electronic systems with a continuously variablesignal. In contrast, in digital electronicssignals usually take only two different levels. The term "analogue" describes the proportional relationship between a signal and a voltage or current that represented the signal.
An analogue signal uses some attribute of the medium to convey the signal's information. For example, an
aneroid barometeruses angularposition as the signal to convey pressureinformation. Electrical signals may represent information by changing their voltage, current, frequency, or total charge. Information is converted from some other physical form ( such as sound, light, temperature, pressure, position) to an electrical signal by a transducer.
The signals take any value from a given range, and each unique signal value represents different information. Any change in the signal is meaningful, and each level of the signal represents a different level of the phenomenon that it represents. For example, suppose the signal is being used to represent temperature, with one
voltrepresenting one degree Celsius. In such a system 10 volts would represent 10 degrees, and 10.1 volts would represent 10.1 degrees.
Another method of conveying an analogue signal is to use
modulation. In this, some base carrier signal has one of its properties altered: amplitude modulation(AM) involves altering the amplitude of a sinusoidal voltage waveform by the source information, frequency modulation(FM) changes the frequency. Other techniques, such as changing the phase of the carrier signal are also used.
In an analogue sound recording, the variation in pressure of a sound striking a
microphonecreates a corresponding variation in the current passing through it or voltage across it. An increase in the volume of the sound causes the fluctuation of the current or voltage to increase proportionally while keeping the same waveformor shape.
pneumatic, hydraulicand other systems may also use analogue signals.
Analogue systems invariably include noise; that is, random disturbances or variations, some caused by the random thermal vibrations of atomic particles. Since all variations of an analogue signal are significant, any disturbance is equivalent to a change in the original signal and so appears as noise. As the signal is copied and re-copied, or transmitted over long distances, these random variations become more significant and lead to signal degradation. Other sources of noise may come from external electrical signals, or poorly designed components. These disturbances are reduced by
shielding, and using low noise amplifiers.
Analogue vs. digital electronics
Since the information is encoded differently in analogue and
digital electronics, the way they process a signal is consequently different. All operations that can be performed on an analogue signal such as amplification, filtering, limiting, and others, can also be duplicated in the digital domain.
The first electronic devices invented and mass produced were analogue. The use of
microelectronicshas reduced the cost of digital techniques and now make digital methods feasible and cost-effective.
The main differences between analogue and digital electronics are listed below:
Because of the way information is encoded in analogue circuits, they are much more susceptible to
noisethan digital circuits, since a small change in the signal can represent a significant change in the information present in the signal and can cause the information present to be lost. Since digital signals take on one of only two different values, a disturbance would have to be about one-half the magnitude of the digital signal to cause an error; this property of digital circuits can be exploited to make signal processing noise-resistant. In digital electronics, because the information is quantized, as long as the signal stays inside a range of values, it represents the same information. Digital circuits use this principle to regenerate the signal at each logic gate, lessening or removing noise.
A number of factors affect how precise a signal is, mainly the noise present in the original signal and the noise added by processing. See
signal-to-noise ratio. Fundamental physical limits such as the shot noisein components limits the resolution of analogue signals. In digital electronics additional precision is obtained by using additional digits to represent the signal; the practical limit in the number of digits is determined by the performance of the analogue to digital converters, since digital operations can usually be performed without loss of precision.
Digital systems are much easier and smaller to design than comparable analogue circuits. This is one of the main reasons why digital systems are more common than analog. An analogue circuit must be designed by hand, and the process is much less automated than for digital systems. Also, because the smaller the
integrated circuit(chip) the cheaper it is, and digital systems are much smaller than analog, therefore a digital system is cheaper to manufacture than an analog one, generally.
Digital- See here for a discussion of digital vs. analog.
Analog sound vs. digital sound
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