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NOISE What is it? Circuit or Environment? zungo qoruboV zhurmë ruido Geräusche Lärm larm bruit vacarme шум شلوغ 噪音

NOISE What is it? Circuit or Environment? zungo qoruboV zhurmë ruido Geräusche Lärm larm bruit vacarme шум شلوغ 噪音 . ELECTRICAL NOISE What is it? A linear variable (voltage or current) for which one does not know the amplitude or the phase with certainty. CONSIDER SHOT NOISE

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NOISE What is it? Circuit or Environment? zungo qoruboV zhurmë ruido Geräusche Lärm larm bruit vacarme шум شلوغ 噪音

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  1. NOISE What is it? Circuit or Environment? zungo qoruboV zhurmë ruido Geräusche Lärm larm bruit vacarme шум شلوغ 噪音

  2. ELECTRICAL NOISE What is it? A linear variable (voltage or current) for which one does not know the amplitude or the phase with certainty.

  3. CONSIDER SHOT NOISE A single electron moving across a region containing an electric field is accelerated. If it encounters multiple collisions so that its velocity is approximately constant over a period of time equal to t, then it generates a current pulse as shown below.

  4. CONSIDER SHOT NOISE, con’t A single electron moving across a region containing an electric field is accelerated. If it travels without encountering collisions its velocity increases over a period of time equal to t , and generates a current pulse as shown below.

  5. CONSIDER SHOT NOISE, con’t A single electron moving across a region containing an electric field is accelerated. One other profile often considered (physical basis = ?) is shown below. Charge transferred is equal to the area under the curve = q.

  6. Normalized power spectral density for the three different pulses. Note that the abscissa could be adjusted for different times versus omega if the effect of a constant length is considered.

  7. Each of the current pulses have a different Fourier Transform. Notice that for small w, all the transforms go to q in value.

  8. The dc current is the average value of the total number of current pulses. For a rate of N pulses per second, the average current is:

  9. The power spectral density of a single current pulse is given by the Fourier transform magnitude squared. Notice however that the value is symmetrical, i.e., the Fourier transform of a pulse is real and F (w)=F (-w). Therefore the two side bands are in phase and will add in phase. Remember cos(x)=cos(-x). Remembering to change from peak to rms amplitudes, the energy in a unit bandwidth for w small is therefore: The power for N of these pulses is: For w small, it doesn’t matter what the shape of the pulses are (see F (w) for the three pulses shapes).

  10. Thermal Noise The rms voltage squared generated by all resistances is given by the next formula. Where h is Planck’s constant = 6.6260755x10-34J-s f is frequency in hertz B is bandwidth in hertz R is resistance in ohms k is Boltzmann’s constant = 1.380658x10-23J/K

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