HPA L2 noise

  1. What sort of distribution does noise tend to have? What is its formula?
    • Gaussian
    • Image Upload 1
  2. What is the formula for root mean square of a noise source? What does this represent?
    Image Upload 2It indicates the normalised power of the signal
  3. What is the formula for power dissipated?
    Image Upload 3Its the same as the root mean noise with units of Volts dissipated over 1ohm. It gets squared so that the units end up as power
  4. What is the noise spectral density? What are its units?
    It describes the noise content in a 1Hz bandwidth. Its got units of V2/Hz.
  5. What does the spectral density function look like?
    Image Upload 4
  6. What do you get by integrating the spectral density function over the region of interest?
    • You end up with the total mean square noise. Notice i didnt say root mean square, so the formula look like this
    • Image Upload 5
  7. what is the mean square noise for white noise?
    Image Upload 6
  8. What is the noise bandwidth?
    The equivalent noise bandwidth is the frequency span of a noise amplitude equal to the peak value and with same total integrated area.
  9. What are the main sources of noise in electrical circuits?
    • Shot noise
    • Thermal (johnson) noise
    • Flicker noise
    • Burst noise
    • Avalanche noise
  10. What is shot noise caused by?
    Current flow across a potential barrier. blah blah
  11. What is the formula for shot noise?
    Image Upload 7
  12. What is the formula for shot noise within a bandwidth?
    Image Upload 8where n is the no. of electrons per second
  13. What is thermal noise? what causes it? What is the formula for the mean square thermal noise voltage?
    • It is noise arising from the thermal fluctuations of free electron.
    • Image Upload 9
    • where k is boltzmann's constant
  14. What can we say about the spectral density function of thermal noise?
    Spectral density function function of thermal noise is flat so it 'white'.
  15. What are the two ways of modelling thermal noise?
    • An ideal noiseless component in series with a thermal voltage vn
    • Or by an equivalent current generator in parallel with a resistance.Image Upload 10
  16. What is flicker noise and what is it caused by?
    • Low frequency phenomenon exhibited by all electronic devices, but nature not understood.
    • Could be due to surface traps capturing and releasing electrons in a random fashion
  17. What is the formula for spectral density function of flicker noise
    Sif(f) = k(Ia/fb) A2/Hz
  18. What is the formula for mean square noise current in a bandwidth for flicker noise?
    if2 = k(ia/fb)Δf  A2 

    where a is around 0.5 and 2 , b is about  and k is an unknown constant.
  19. What is burst noise (popcorn noise), and what causes it
    Occurs in all semiconductor devices and is sudden changes in the average level of the already existing noise (noise of noise)

    If  a noise signal is amplified and fed to loudspeakers, you get a constant and random crackle.

    Burst noise is common in monolithic IC amps but its causes are unknown.
  20. What is avalanche noise? What is it caused by?
    Produced by zener/avalanche breakdown during the reverse biasing of a pn junction. 

    Carriers in the depletion region create electron/hole pairs by colliding with silicon atoms. 

    Avalanche noise is much greater than shot noise, so zener diodes are avoided in low-noise designs.
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HPA L2 noise
high performance analog lecture 2 noise