Analogue electronics

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Analogue electronic components like this thermistor function with continuous signals, unlike digital electronics which have discrete signals, usually binary code

Analogue electronics (American English : analog electronics) are electronic systems with a continuously variable signal, in contrast to digital electronics where signals usually take only two levels. The term analogue describes the proportional relationship between a signal and a voltage or current that represents the signal. The word analogue is derived from the Greek word ανάλογοςanalogos meaning proportional. [1]

Contents

Analogue signals

An analogue signal uses some attribute of the medium to convey the signal's information. For example, an aneroid barometer uses the angular position of a needle on top of a contracting and expanding box as the signal to convey the information of changes in atmospheric pressure. [2] 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 which converts one type of energy into another (e.g. a microphone). [3]

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 volt representing 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 phase modulation or changing the phase of the carrier signal, are also used. [4]

In an analogue sound recording, the variation in pressure of a sound striking a microphone creates 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 waveform or shape.

Mechanical, pneumatic, hydraulic, and other systems may also use analogue signals.

Inherent noise

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. [5] 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 include crosstalk from other signals or poorly designed components. These disturbances are reduced by shielding and by using low-noise amplifiers (LNA). [6]

Analogue vs digital electronics

A digital signal like USB is inherently an analogue signal USB signal example.svg
A digital signal like USB is inherently an analogue signal

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. Every digital circuit is also an analogue circuit, in that the behaviour of any digital circuit can be explained using the rules of analogue circuits.

The use of microelectronics has made digital devices cheap and widely available.

Noise

The effect of noise on an analogue circuit is a function of the level of noise. The greater the noise level, the more the analogue signal is disturbed, slowly becoming less usable. Because of this, analogue signals are said to "fail gracefully". Analogue signals can still contain intelligible information with very high levels of noise. Digital circuits, on the other hand, are not affected at all by the presence of noise until a certain threshold is reached, at which point they fail catastrophically. For digital telecommunications, it is possible to increase the noise threshold with the use of error detection and correction coding schemes and algorithms. Nevertheless, there is still a point at which catastrophic failure of the link occurs. [7] [8]

In digital electronics, because the information is quantized, as long as the signal stays inside a range of values, it represents the same information. In digital circuits the signal is regenerated at each logic gate, lessening or removing noise. [9] [ failed verification ] In analogue circuits, signal loss can be regenerated with amplifiers. However, noise is cumulative throughout the system and the amplifier itself will add to the noise according to its noise figure. [10] [11]

Precision

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 noise in 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 converter (ADC), since digital operations can usually be performed without loss of precision. The ADC takes an analogue signal and changes it into a series of binary numbers. The ADC may be used in simple digital display devices, e. g., thermometers or light meters but it may also be used in digital sound recording and in data acquisition. However, a digital-to-analogue converter (DAC) is used to change a digital signal to an analogue signal. A DAC takes a series of binary numbers and converts it to an analogue signal. It is common to find a DAC in the gain-control system of an op-amp which in turn may be used to control digital amplifiers and filters. [12]

Design difficulty

Analogue circuits are typically harder to design, requiring more skill than comparable digital systems to conceptualize. [13] An analogue circuit is usually designed by hand because the application is built into the hardware. Digital hardware, on the other hand, has a great deal of commonality across applications and can be mass-produced in a standardised form. Hardware design consists largely of repeated identical blocks and the design process can be highly automated. This is one of the main reasons that digital systems have become more common than analogue devices. However, the application of digital hardware is a function of the software/firmware and creating this is still largely a labour-intensive process. Since the early 2000s, there were some platforms that were developed which enabled analogue design to be defined using software - which allows faster prototyping. Furthermore, if a digital electronic device is to interact with the real world, it will always need an analogue interface. [14] For example, every digital radio receiver has an analogue preamplifier as the first stage in the receive chain.

Design of analogue circuits has been greatly eased by the advent of software circuit simulators such as SPICE. IBM developed their own in-house simulator, ASTAP, in the 1970s which used an unusual (compared to other simulators) sparse matrix method of circuit analysis.

Circuit classification

Analogue circuits can be entirely passive, consisting of resistors, capacitors and inductors. Active circuits also contain active elements such as transistors. Traditional circuits are built from lumped elements – that is, discrete components. However, an alternative is distributed-element circuits, built from pieces of transmission line.

See also

Related Research Articles

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<span class="mw-page-title-main">Analog computer</span> Computer that uses continuously varying data technology

An analog computer or analogue computer is a type of computer that uses the continuous variation aspect of physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved. In contrast, digital computers represent varying quantities symbolically and by discrete values of both time and amplitude.

<span class="mw-page-title-main">Electronics</span> Branch of physics and electrical engineering

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<span class="mw-page-title-main">Analog-to-digital converter</span> System that converts an analog signal into a digital signal

In electronics, an analog-to-digital converter is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide an isolated measurement such as an electronic device that converts an analog input voltage or current to a digital number representing the magnitude of the voltage or current. Typically the digital output is a two's complement binary number that is proportional to the input, but there are other possibilities.

<span class="mw-page-title-main">Comparator</span> Device that compares two voltages or currents

In electronics, a comparator is a device that compares two voltages or currents and outputs a digital signal indicating which is larger. It has two analog input terminals and and one binary digital output . The output is ideally

<span class="mw-page-title-main">Delta modulation</span> Signal conversion technique

Delta modulation is an analog-to-digital and digital-to-analog signal conversion technique used for transmission of voice information where quality is not of primary importance. DM is the simplest form of differential pulse-code modulation (DPCM) where the difference between successive samples is encoded into n-bit data streams. In delta modulation, the transmitted data are reduced to a 1-bit data stream representing either up (↗) or down (↘). Its main features are:

A signal generator is one of a class of electronic devices that generates electrical signals with set properties of amplitude, frequency, and wave shape. These generated signals are used as a stimulus for electronic measurements, typically used in designing, testing, troubleshooting, and repairing electronic or electroacoustic devices, though it often has artistic uses as well.

<span class="mw-page-title-main">Digital-to-analog converter</span> Device that converts a digital signal into an analog signal

In electronics, a digital-to-analog converter is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function.

<span class="mw-page-title-main">Modular synthesizer</span> Synthesizer composed of separate modules

Modular synthesizers are synthesizers composed of separate modules for different functions. The modules can be connected together by the user to create a patch. The outputs from the modules may include audio signals, analog control voltages, or digital signals for logic or timing conditions. Typical modules are voltage-controlled oscillators, voltage-controlled filters, voltage-controlled amplifiers and envelope generators.

<span class="mw-page-title-main">Signal</span> Varying physical quantity that conveys information

Signal refers to both the process and the result of transmission of data over some media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processing, information theory and biology.

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<span class="mw-page-title-main">Sample and hold</span> Type of voltage sampling device

In electronics, a sample and hold circuit is an analog device that samples the voltage of a continuously varying analog signal and holds its value at a constant level for a specified minimum period of time. Sample and hold circuits and related peak detectors are the elementary analog memory devices. They are typically used in analog-to-digital converters to eliminate variations in input signal that can corrupt the conversion process. They are also used in electronic music, for instance to impart a random quality to successively-played notes.

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<span class="mw-page-title-main">Mixed-signal integrated circuit</span> Integrated circuit

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<span class="mw-page-title-main">Delta-sigma modulation</span> Method for converting signals between digital and analog

Delta-sigma modulation is an oversampling method for encoding signals into low bit depth digital signals at a very high sample-frequency as part of the process of delta-sigma analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). Delta-sigma modulation achieves high quality by utilizing a negative feedback loop during quantization to the lower bit depth that continuously corrects quantization errors and moves quantization noise to higher frequencies well above the original signal's bandwidth. Subsequent low-pass filtering for demodulation easily removes this high frequency noise and time averages to achieve high accuracy in amplitude which can be ultimately encoded as pulse-code modulation (PCM).

<span class="mw-page-title-main">Class-D amplifier</span> Audio amplifier based on switching

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Effective number of bits (ENOB) is a measure of the dynamic range of an analog-to-digital converter (ADC), digital-to-analog converter, or their associated circuitry. The resolution of an ADC is specified by the number of bits used to represent the analog value. Ideally, a 12-bit ADC will have an effective number of bits of almost 12. However, real signals have noise, and real circuits are imperfect and introduce additional noise and distortion. Those imperfections reduce the number of bits of accuracy in the ADC. The ENOB describes the effective resolution of the system in bits. An ADC may have a 12-bit resolution, but the effective number of bits, when used in a system, may be 9.5.

<span class="mw-page-title-main">Electronic engineering</span> Electronic engineering involved in the design of electronic circuits, devices, and their systems

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<span class="mw-page-title-main">Digital signal</span> Signal used to represent data as a sequence of discrete values

A digital signal is a signal that represents data as a sequence of discrete values; at any given time it can only take on, at most, one of a finite number of values. This contrasts with an analog signal, which represents continuous values; at any given time it represents a real number within a continuous range of values.

The following outline is provided as an overview of and topical guide to electronics:

References

  1. ↑ Concise Oxford dictionary (10 ed.). Oxford University Press Inc. 1999. ISBN   0-19-860287-1.
  2. ↑ Plympton, George Washington (1884). The aneroid barometer: its construction and use. D. Van Nostran Co. aneroid barometer.
  3. ↑ Singmin, Andrew (2001). Beginning Digital Electronics Through Projects. Newnes. p. 9. ISBN   0-7506-7269-2. Signals come from transducers...
  4. ↑ Miller, Mark R. (2002). Electronics the Easy Way . Barron's Educational Series. pp.  232–239. ISBN   0-7641-1981-8. Until the radio came along...
  5. ↑ Hsu, Hwei Piao (2003). Schaum's Outline of Theory and Problems of Analogue and Digital Communications. McGraw-Hill Professional. p. 202. ISBN   0-07-140228-4. The presence of noise degrades the performance of communication systems.
  6. ↑ Carr, Joseph J. (2000). Secrets of RF circuit design. McGraw-Hill Professional. p. 423. ISBN   0-07-137067-6. It is common in microwave systems...
  7. ↑ Richard Langton Gregory, Even Odder Perceptions, p. 161, Psychology Press, 1994 ISBN   0415061067.
  8. ↑ Robin Blair, Digital Techniques in Broadcasting Transmission, p. 34, Focal Press, 2002, ISBN   0240805089.
  9. ↑ Chen, Wai-Kai (2005). The electrical engineering handbook. Academic Press. p. 101. ISBN   0-12-170960-4. Noise from an analogue (or small-signal) perspective...
  10. ↑ Jon B. Hagen, Radio-Frequency Electronics: Circuits and Applications, p. 203, Cambridge University Press, 1996 ISBN   0521553563.
  11. ↑ Jonathan Davidson, James Peters, Brian Gracely, Voice Over IP Fundamentals, Cisco Press, 2000 ISBN   1578701686.
  12. ↑ Scherz, Paul (2006). Practical electronics for inventors. McGraw-Hill Professional. p. 730. ISBN   0-07-145281-8. In order for analog devices... to communicate with digital circuits...
  13. ↑ "Clocks - Digital and Analog". Math is Fun. Retrieved 2020-12-18.
  14. ↑ Williams, Jim (1991). Analog circuit design. Newnes. p. 238. ISBN   0-7506-9640-0. Even within companies producing both analog and digital products...
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