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Unformatted text preview: 63 Noise in Integrated Circuits Fundamental Noise Sources Thermal Noise (Johnson Noise, Nyquist Noise) arises from thermally excited random motion of electrons in a conductive medium Properties of thermal noise 1) noise is white (?) 2) noise is proportional to temperature 3) not associated with DC current 4) can find it in any real physical resistor f Noise Spectral Density Representation of thermal noise R R 2 R i or 2 R v R does not mean the current is in certain direction 64 in fact average current (or voltage) is zero V(t) i(t) or t but you can go to frequency domain and plot meansquare value of the noise signal f 2 R i f 2 R v noise spectral density f R kT i R ∆ = 4 2 f kTR v R ∆ = 4 2 bandwidth of interest (ckt or measurement) = = R R v i noise average is zero but average noise power is not?! why f kTR v R ∆ = 4 2 assume a simple ckt of parallel RC 65 2 C v 2 R v R C noiseless capacitor An equipartition theorem of statistical thermodynamic for each degree of freedom (or mode) in a given system, there is a thermal energy of kT 2 1 k: Boltzmann constant K J 23 10 38 . 1 × Total energy of the system 2 2 1 2 1 C v C kT = = C kT v C = 2 total mean square voltage density integrated over all frequencies 66 C kT df f v RC j v R C = ∆ + = ∫ ∞ 2 2 2 1 1 w filtering function f v R ∆ 2 f constant white noise f v R ∆ 2 f nonwhite R V R C C V Assuming white noise = R v R 2 constant w w w w p d f v C kT R ∫ ∞ + ∆ = 2 2 2 2 2 RC 1 = w...
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This note was uploaded on 02/19/2012 for the course ECE 455 taught by Professor Mohammadi during the Fall '10 term at Purdue University.
 Fall '10
 Mohammadi
 Integrated Circuit

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