# Noise

#### loity

Joined Jun 1, 2004
2
Please can someone give me some values of various noises in semiconductors in decibels. The type of noise in question is shot, partition, thermal agitation, flicker and also some reference to crosstalk and interference, also the effects of noise on circuits.
Loity

#### mozikluv

Joined Jan 22, 2004
1,437
hi,

am not going to give you the full details of your assignment but rather just give you a birds eye view of what you are asking.

thermal noise is cause by thermal agitation of electrons in a device
and can be computed by using Nyquist relation formula;
V^2R = 4K x T x R x f
V^2R = mean square of noise voltage
K = Boltzmann constant ( 1.38E-23
T = Kelvin temp.
R = resistance in ohms
f = noise bandwidth in Hertz

shot noise or white noise is cause by changes in molecular energy level while the device conducts

flicker noise is a low frequency effect, the lower the freq. the higher the noise. ( I/f )

dBv refers to decibles relative to 1vrms
dBu refers to decibles relative to 775mv
0dBv = +2.2dBu

interference is usualy\ly cause by RF signals, motor hum, static and many more.

op-amp noise figure is usually expressed in ( nV / sq. rt. of frequency)

doing research will give you a cleare picture h34r:

check this site:oscillators