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Noise Is Widespread NoiseNoise A definition (not mine) Electrical Noise S. Oberholzer and E. Bieri (Basel) T. Kontos and C. Hoffmann (Basel) A. Hansen and B-R Choi (Lund and Basel) ¾ Electrical noise is defined as any undesirable electrical energy (?) T. Akazaki and H. Takayanagi (NTT) E.V. Sukhorukov and D. Loss (Basel) C. Beenakker (Leiden) and M. Büttiker (Geneva) T. Heinzel and K. Ensslin (ETHZ) M. Henny, T. Hoss, C. Strunk (Basel) H. Birk (Philips Research and Basel) Effect of noise on a signal. (a) Without noise (b) With noise ¾ we like it though (even have a whole conference on it) National Center on Nanoscience Swiss National Science Foundation 1 2 Noise may have been added to by ... Introduction: Noise is widespread Noise (audio, sound, HiFi, encodimg, MPEG) Electrical Noise Noise (industrial, pollution) Noise (in electronic circuits) Noise (images, video, encoding) Noise (environment, pollution) it may be in the “source” signal from the start Noise (radio) it may have been introduced by the electronics Noise (economic => theory of pricing with fluctuating it may have been added to by the envirnoment source terms) it may have been generated in your computer Noise (astronomy, big-bang, cosmic background) Noise figure Shot noise Thermal noise for the latter, e.g. sampling noise Quantum noise Neuronal noise Standard quantum limit and more ... 3 4 Introduction: Noise is widespread Introduction (Wikipedia) Noise (audio, sound, HiFi, encodimg, MPEG) Electronic Noise (from Wikipedia) Noise (industrial, pollution) Noise (in electronic circuits) Noise (images, video, encoding) Electronic noise exists in any electronic circuit as a result of random variations in current or voltage caused by the random movement of the Noise (environment, pollution) electrons carrying the current as they are jolted around by thermal energy.energy Noise (radio) The lower the temperature the lower is this thermal noise. Noise (economic => theory of pricing with fluctuating source terms) This same phenomenon limits the minimum signal level that any radio receiver can usefully respond to, because there will always be a small but significant Noise (astronomy, big-bang, cosmic background) amount of thermal noise arising in its input circuits. This is why radio telescopes, Noise figure which search for very low levels of signal from stars, use front-end ciruits, usually mounted on the aerial dish, cooled in liquid nitrogen to a very low Shot noise Î focus on Noise in temperature. Electronic Circuits Thermal noise Electronic Circuits Quantum noise Neuronal noise Standard quantum limit and more ... 5 6 Introduction (Wikipedia) Introduction: spectra of a „small“ signal Electronic noise is often measured in μV/√Hz, a term that derives from the fact that doubling the bandwidth of the measurement doubles the power level measured, but voltage is proportional to the square root of power. Integrated circuit devices, such as op-amps commonly quote equivalent input noise level in these terms (at room temperature). Î white noise 7 8 Introduction (Wikipedia) Introduction (Wikipedia) Thermal Noise (from Wikipedia) Shot Noise also from Wikipedia Johnson-Nyquist noise (thermal noise, Johnson noise, or Nyquist noise) is the noise generated by the equilibrium fluctuations of the electric current inside an electrical conductor, which happens regardless of any applied voltage, due Shot noise is a type of noise that occurs when the finite number of particles that to the random thermal motion of the charge carriers (the electrons). carry energy, such as electrons in an electronic circuit or photons in an optical device, gives rise to detectable statistical fluctuations in a measurement. It is It was first measured by J. B. Johnson at Bell Labs in 1928. He described important in electronics, telecommunications and fundamental physics. his findings to H. Nyquist, also at Bell Labs, who was able to explain the results by deriving a fluctuation-dissipation relationship. The strength of this noise increases with the average magnitude of the current or Thermal noise is to be distinguished from shot noise, which consists of intensity of the light. Often, however, as the signal increases more rapidly as the additional current fluctuations that occur when a voltage is applied and a average signal becomes stronger, shot noise often is only a problem with small macroscopic current starts to flow. For the general case, the above definition currents and light intensities. applies to charge carriers in any type of conducting medium (e.g. ions in an electrolyte). Nyquist Schottky 9 10 Introduction (Wikipedia) Introduction (Wikipedia) Shot Noise also from Wikipedia Shot Noise also from Wikipedia Shot noise is a type of noise that occurs when the finite number of particles that Shot noise is a type of noise that occurs when the finite number of particles that carry energy, such as electrons in an electronic circuit or photons in an optical carry energy, such as electrons in an electronic circuit or photons in an optical device, gives rise to detectable statistical fluctuations in a measurement. It is device, gives rise to detectable statistical fluctuations in a measurement. It is important in electronics, telecommunications and fundamental physics. important in electronics, telecommunications and fundamental physics. The strength of this noise increases with the average magnitude of the current or The strength of this noise increases with the average magnitude of the current or intensity of the light. Often, however, as the signal increases more rapidly as the intensity of the light. Often, however, as the signal increases more rapidly as the average signal becomes stronger, shot noise often is only a problem with small average signal becomes stronger, shot noise often is only a problem with small currents and light intensities. currents and light intensities. what would the author likely like to say? input by a reader: for example, as the rms number fluctuations grow slower than the average “Shot noise and thermal noise have long been believed to be the results of distinct number (i.e. like the square of N in a Poissonian process), noise is only a mechanisms but they aren't. Thermal noise is shot noise due to internal problem for small numbers (i.e. small signals). diffusion currents in electronic devices… Shot noise is shot noise. The main result is illustrated in these measured and theoretical results for noise in subthreshold MOS transistors ….” 11 12 Introduction (Shot Noise on Wikipedia) Introduction (Shot Noise on Wikipedia) Shot noise in electronic devices consists of random fluctuations of the electric Shot noise is a type of noise that occurs when the finite number of particles current in an electrical conductor, which are caused by the fact that the current is that carry energy, such as electrons in an electronic circuit or photons in an optical carried by discrete charges (electrons). device, gives rise to detectable statistical fluctuations in a measurement. It is important in electronics, telecommunications and fundamental physics. Shot noise is to be distinguished from current fluctuations in equilibrium (Johnson- Nyquist noise). I thought shot noise was to do with electrons passing over a junction between two different conducting materials? … I’ll go else where and check... [email protected] Shot noise is a Poisson process and the charge carriers which make up the current will follow a Poisson distribution. The strength of the current fluctuations can I think that's called a flicker noise... [email protected] be expressed by giving the variance Hi, 2 2 Δ I := ()I − I You are absolutely right, and this page needs some editing. I think I or someone with more detailed knowledge should do this. of the current I, where <I> is the average ("macroscopic") current. Briefly speaking, the granular nature of charge is not responsible for shot noise by itself. Shot noise occurs when charge carriers must cross a junction. However, the value measured in this way depends on the frequency range of So for instance, a copper wite carrying current will exhibit only thermal noise but not shot fluctuations which is measured (bandwidth): The measured variance of the noise, while a semiconductor junction will exhibit both. current grows linearly with bandwidth. Therefore, a more fundamental quantity is the noise power, which is essentially obtained by dividing through the bandwidth Flicker noise is an altogether different phenomenon, and while there are several theories (and, therefore, has the SI units Ampere squared divided by Hertz). and models regarding flicker noise, there is no universally accepted physical model to explain it yet (perhaps a Nobel Prize waiting for someone), despite and perhaps owing to its universal nature. It is seen in phenomena from microscopic scale to the astronomical scale. Vivek vivkr.at.yahoo.com 13 14 Vacuum Tube: its implication to flicker noise Vacuum Tube: a comment "The triode was invented by Lee de Forest in 1907, and soon afterwards the first amplifiers were built. By 1921 the 'thermionic tube' amplifiers were so developed that C.A. Hartmann made the first courage experiment to verify Schottky's formula for ths shot noice spectral density. Hartmann's attempt failed (that’s not fully true, though), and it was finally J.B. taken from R.E. Burgess et al., British Journal of Appl. Phys., Vol. 6 (1955) Johnson who successfully measured the predicted white noise spectrum. However, Johnson also measured an unexpected 'flicker noise' at low frequency... and shortly thereafter W. Schottly tried to provide a theoretical explanation. Schottky's explanation was based on the physics of electron transport inside the vacumm tube, but in the years that followed Johnson's discovery of flicker noise, it was found that this strange noise appeared again and again in many different electrical deviced." 15 16 Introduction (Flicker Noise on Wikipedia) Introduction (Flicker Noise on Wikipedia) Pink noise, also known as 1/f noise, is a signal or process with a frequency spectrum such that the power spectral density is proportional to the reciprocal of Some researchers describe it is as being ubiquitous.
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