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	== Origin of term ==		== Origin of term ==
	The word "analog" implies an ] between the input and output variables , and the signal voltages and currents in the circuit. An '''analog circuit''' is therefore an ] that operates on ]s.

			The word "analog" implies an ] between the variations in the signal and variations in the phenomena that produces that signal. So, the signal is analogus to the natural phenomena, unlike digital signals.
	== Explanation ==
	Analog electronics is sometimes confused with other sub-divisions of the general field of Electronics which include ] and ].

	=== Analogs ===
	The word "analog" implies an ] between signal level, and ]s or currents in the circuit.

		⚫	== Analog signals ==
	For example, in an analog 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 or amplitude of the sound causes the fluctuation of the current or voltage to increase proportionally while keeping the same ] or shape and electrical analog.

	]s with hands are often called analog displays; those that display digits are usually called digital displays. However, many analog clocks are actually digital since the hands do not move in a smooth continuous motion, but in small steps every second or sub division of a second.

			Analog signals are signals that have two characteristics. They can take ANY value from a given range, and each unique signal value represents a different information. Simply put, small changes in the signal are meaningful, and each value of the signal translates differently, if the signal represents temperature into a diferent temperature, if it represent the amount of light of a given color, into a diferent amount of light, etc.
	In the field of Power Electronics analogs can be the Energy Storing variables such as the current in an Inductor or the Voltage across the terminals of a ].
			For example, analog thermometers measure temperature and usually produce a voltage that changes linealy with temperature. In this exmaple, the information of interest is the temperature, and is represented by the voltage, so if the the temperature rises, the voltage will increase, and vice versa. We know this signal is analog because each voltage represents a unique temperature. In digital electronics, different voltage levels can represent the same information(the same temperature), which is known as quantization.

			Analog signals can have the information of interest represented by current, voltage, frecuency, phase, etc. Analog refers only to the fact that each value in the signal corresponds to a unique value of the information of interest. To better understand analog signals, a rudimentary understanding of digital signals is prefered, as ] are the counterpart to analog circuits.
	===Information and analog signals ===
	Any information may be conveyed by an analog signal, often such a signal is a measured response to changes in physical phenomena, such as sound, light, temperature, position, or pressure, and is achieved using a ]. An analog signal uses some property of the medium to convey the signal's information. For example, an ] ] uses ] position as the signal to convey ] information. ]ally, the property most commonly used is voltage followed closely by ], current, and charge.

			The basic building block of analog circuits is the operational amplifier, since it can perform such a large number of functions useful in analog electronics, including addition, substraction, multiplication, division, integration, differentiation and magnitude comparations.
	Another method of conveying an analog signal is to use ]. In this, some base signal (e.g., a ] carrier wave) has one of its properties altered: ] involves altering the amplitude of a sinusoidal voltage waveform by the source information, ] changes the frequency. Other techniques, such as changing the phase of the base signal do also work.

	Analog circuits do not involve quantisation of information into digital format. The source signal information being measured over the circuit, whether sound, light, pressure, temperature, or an exceeded limit, remains continuous from end to end.
	See ] for a discussion of digital vs. analog.

	== Analog ~~operations~~ ==		== Analog and Digital Electronics==
	While operating on an analog signal, an analog circuit changes the signal in some manner or manners. It may be designed to ], ], provide ], ], or modify the signal in some other way. It can be used to convert the signal into some other format such as a ] signal. Analog circuits also modify signals in unintended ways such as adding noise or distortion.

			Since the infromation is encoded very differently in analog and digital electronics, the way they process a signal is consecuetly very different. Hoever, most operations that can be done to an analog signal can also be done to a digital signal but in a different way.
	Analog Electronics is frequently confused with other sub-divisions of the general field of Electronics which include Power electronics and Digital electronics. Or in the field of Power Electronics can be the Energy Storing variables such as the current in an Inductor or the Voltage across the terminals of a Capacitor.
	Any information may be conveyed by an analog signal, often such a signal is a measured response to changes in physical phenomena, such as sound, light, temperature, position, or pressure, and is achieved using a transducer.

			The first electronic devices invented and mass produced were analog. However, as time progressed digital circuits have become predominant in electronics. It is important to note that analog and digital devices are the same, the only diference is the way represent and process information. The same basic components for a circuit can be used for analog or digital cirucits.
⚫	== Analog signals ==

	An analog signal uses some property of the medium to convey the signal's information. For example, an aneroid barometer uses rotary position as the signal to convey pressure information. Electrically, the property most commonly used is voltage followed closely by frequency, current, and charge.

			The main diferences between analog and digital electronics are listed below:



			'''Noise:''' Because the way information is encoded in analog circuits, they are much more suceptible to noise than digital circuits, since a small change in the signal can represent a very large change in the information present in the signal and can cause the information present to be lost, corrupt or useless. In digital electronics, because the information is quantized, as long as the signal stays inside a range of values, it represents the same information. This is one of the main reasons digital electronics are predominant. In fact, digital circuits use this principle to regenerate the signal at each logic gate, lessening or removing noise.


			'''Precision:''' A lot of factors afect how precice a signal is, mainly the noise present in the original signal and the noise added by the processing stage. See ]. In digital electronics it is much easier to have high pressision signals than in analog electronics, because of the way information is represented and how noise afects digital and analog signals.

	For example, in an analog 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 or amplitude of the sound causes the fluctuation of the current or voltage to increase proportionally while keeping the same waveform or shape and electrical analog.

			'''Speed:''' This is where analog electronics really outshines digital electronics. Analog ciruits are several times faster than their digital counterparts. Depending on the operation, analog circuits can be several, hundreds or hundreds of thousands of times faster digital circuits. This is because information in digital circuits is represented by bits, while in analog electronics it is represented by property of the signal itself. So, if you need to transmit the digital signal you have to send 64 bits, usually sending one bit after another. The same signal in analog electronics could easily be represented by a voltage, and transmiting that voltage takes the same time to transmit than one bit, so the analog signal in the example is at least 64 times faster than digital.
	=== Noise ===
	{{Main\|Electronic noise}}
	The effects of random noise can make signal loss and distortion impossible to recover, since amplifying the signal to recover attenuated parts of the signal often generates more noise and amplifies the noise as well.

	Another method of conveying an analog signal is to use modulation. In this, some base signal (e.g., a sinusoidal carrier wave) has one of its properties altered: amplitude modulation involves altering the amplitude of a sinusoidal voltage waveform by the source information, frequency modulation changes the frequency. Other techniques, such as changing the phase of the base signal do also work.

			'''Bandwith:''' Simply put, bandwith is the amount of information a given circuit can cope with. One again, analog is has much more bandwith than digital, and can process/transmit more information in the same time.
	Analog circuits do not involve quantisation of information into digital format. The source signal information being measured over the circuit, whether sound, light, pressure, temperature, or an exceeded limit, remains continuous from end to end.

			'''Design Dificulty:''' Digital systems are much easier and smaller to design than comparable analog circuits. This is one of the main reasons why digital sistems are more common than analog. An analog 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 chipper it is, and digital sistems are much smaller than analog, digital is cheaper to manufacture.
	Clocks with hands are often called analog displays; those that display digits are usually called digital displays. However, many analog clocks are actually digital since the hands do not move in a smooth continuous motion, but in small steps every second or sub division of a second.

	== Passive versus active ==
	Passive analog circuits consume no external electrical power while active analog circuits use an electrical power source to achieve the designer's goals. An example of a passive analog circuit is a ] that limits the amplitude at some frequencies
	vs. others. A similar example of an active analog circuit is an ]. It does a similar job only it uses an ] to accomplish a similar task.

			== Future of Analog Electronics ==
	Advantages of a passive analog circuit are it requires no power source, gives off less heat, and may produce less noise. Advantages of an active analog circuit is it can load the signal less, amplify as well as attenuate the signal and by using capacitors in combination with amplifiers it can simulate an inductor. Simulation of inductions has the advantage of reducing weight and cost.

			The field of analog electronics nowdays deals with high speed, high performance devices that need the unique advantages provided by analog circuits. Also, digital circuits are an abstraction of analog circuits, but remain analog circuits. As technology progressses and transistors get smaller and smaller, it becomes more and more important to incorporate effects usually present only in analog circuits to digital circuits, and will require expertise on analog circuits.
	===Analog integrated circuit===
	{{main\|Analog chip}}
	Active or passive analog electronic circuits can be fabricated directly onto ] substrates, such as ]. Such circuits are called analog ]s. They may occur as sub-systems of other digital systems (e.g., an analog comparator in a microcontroller.) Analog ] is a highly specialized area.
	== Disadvantages of analog systems ==
	The primary disadvantage of analog signalling is that any system has ] (random disturbances or variations) in it. As the signal is copied and re-copied, or transmitted over long distances, these random variations accumulate and lead to signal degradation. Electrically this noise can be lessened by ], good connections, special cable types such as ] and ], and using low noise amplifiers. The effects of random noise can make signal loss and distortion impossible to recover, since amplifying the signal to recover attenuated parts of the signal often generates more noise and amplifies the noise as well.

			Analog electronics will probably continue reducing its aplications, that will be replaced by digital circuits because of their smaller size, cheaper cost and easer design. Analog electronics will never cease to exist, but will continue to exist as an speciality field for high performance circuits, or as a high performance part of a digital chip, as integrated circuits with analog and digital circuits in the same substrate become more popular.
	Sources: Some of an earlier version of this article was originally taken from Federal Standard 1037C in support of MIL-STD-188.

	== Analog circuit functions ==		== Analog circuit functions ==

Revision as of 04:26, 18 September 2006

Analog circuit (or analogue circuit) refers to electronics systems with analog signals with any continuously variable signal. It differs from digital electronics in that small fluctuations in the signal are meaningful in that they are continuously variable rather than digitally quantised.

Origin of term

The word "analog" implies an analogy between the variations in the signal and variations in the phenomena that produces that signal. So, the signal is analogus to the natural phenomena, unlike digital signals.

Analog signals

Analog signals are signals that have two characteristics. They can take ANY value from a given range, and each unique signal value represents a different information. Simply put, small changes in the signal are meaningful, and each value of the signal translates differently, if the signal represents temperature into a diferent temperature, if it represent the amount of light of a given color, into a diferent amount of light, etc. For example, analog thermometers measure temperature and usually produce a voltage that changes linealy with temperature. In this exmaple, the information of interest is the temperature, and is represented by the voltage, so if the the temperature rises, the voltage will increase, and vice versa. We know this signal is analog because each voltage represents a unique temperature. In digital electronics, different voltage levels can represent the same information(the same temperature), which is known as quantization.

Analog signals can have the information of interest represented by current, voltage, frecuency, phase, etc. Analog refers only to the fact that each value in the signal corresponds to a unique value of the information of interest. To better understand analog signals, a rudimentary understanding of digital signals is prefered, as digital circuits are the counterpart to analog circuits.

The basic building block of analog circuits is the operational amplifier, since it can perform such a large number of functions useful in analog electronics, including addition, substraction, multiplication, division, integration, differentiation and magnitude comparations.

Analog and Digital Electronics

Since the infromation is encoded very differently in analog and digital electronics, the way they process a signal is consecuetly very different. Hoever, most operations that can be done to an analog signal can also be done to a digital signal but in a different way.

The first electronic devices invented and mass produced were analog. However, as time progressed digital circuits have become predominant in electronics. It is important to note that analog and digital devices are the same, the only diference is the way represent and process information. The same basic components for a circuit can be used for analog or digital cirucits.

The main diferences between analog and digital electronics are listed below:

Noise: Because the way information is encoded in analog circuits, they are much more suceptible to noise than digital circuits, since a small change in the signal can represent a very large change in the information present in the signal and can cause the information present to be lost, corrupt or useless. In digital electronics, because the information is quantized, as long as the signal stays inside a range of values, it represents the same information. This is one of the main reasons digital electronics are predominant. In fact, digital circuits use this principle to regenerate the signal at each logic gate, lessening or removing noise.

Precision: A lot of factors afect how precice a signal is, mainly the noise present in the original signal and the noise added by the processing stage. See Signal to Noise Ratio. In digital electronics it is much easier to have high pressision signals than in analog electronics, because of the way information is represented and how noise afects digital and analog signals.

Speed: This is where analog electronics really outshines digital electronics. Analog ciruits are several times faster than their digital counterparts. Depending on the operation, analog circuits can be several, hundreds or hundreds of thousands of times faster digital circuits. This is because information in digital circuits is represented by bits, while in analog electronics it is represented by property of the signal itself. So, if you need to transmit the digital signal you have to send 64 bits, usually sending one bit after another. The same signal in analog electronics could easily be represented by a voltage, and transmiting that voltage takes the same time to transmit than one bit, so the analog signal in the example is at least 64 times faster than digital.

Bandwith: Simply put, bandwith is the amount of information a given circuit can cope with. One again, analog is has much more bandwith than digital, and can process/transmit more information in the same time.

Design Dificulty: Digital systems are much easier and smaller to design than comparable analog circuits. This is one of the main reasons why digital sistems are more common than analog. An analog 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 chipper it is, and digital sistems are much smaller than analog, digital is cheaper to manufacture.

Future of Analog Electronics

The field of analog electronics nowdays deals with high speed, high performance devices that need the unique advantages provided by analog circuits. Also, digital circuits are an abstraction of analog circuits, but remain analog circuits. As technology progressses and transistors get smaller and smaller, it becomes more and more important to incorporate effects usually present only in analog circuits to digital circuits, and will require expertise on analog circuits.

Analog electronics will probably continue reducing its aplications, that will be replaced by digital circuits because of their smaller size, cheaper cost and easer design. Analog electronics will never cease to exist, but will continue to exist as an speciality field for high performance circuits, or as a high performance part of a digital chip, as integrated circuits with analog and digital circuits in the same substrate become more popular.

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