This is an old revision of this page, as edited by NightHawk 099 (talk | contribs) at 04:26, 18 September 2006. The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.
Revision as of 04:26, 18 September 2006 by NightHawk 099 (talk | contribs)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)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.
Analog circuit functions
- Analog multipliers
- electronic amplifiers
- electronic filters
- electronic oscillators
- Phase-locked loops
- electronic mixers
- Power conversion
- Electronic power supply
- impedance matchers
- operational amplifiers
- comparators
- Voltage regulators