Noise spectral density

The generation of photons obeys Poisson statistics where the variance is N and the deviation or noise is. The noise spectral density, N/, is obtained by a Fourier transform of the deviation yielding the following at sampling frequency,... 

Resolution can only be determined after noise evaluation of the sensor, keeping in mind that noise is related to the operating point. In practical situations different kinds of noises can be encountered Thermal, Flicker, Generation-Recombination, Shot, and others that are seen in special cases but are not so frequent. The most important parameter used for the characterization of noise devices is the Noise Spectral Density by which, through integration, it is possible to estimate the mean square value of the output voltage ... 

Noise correlation function, 22 113 Noise equivalent power (NEP), 19 133 Noise spectral density, 19 134-135 Nomarski, Georges, 16 480 Nomarski-modified Wollaston prism, 16 481... 

We present the theoretical overview first for the case of voltage bias [1]. In a junction with a low transparency barrier (which corresponds to our samples) biased by a dc voltage V, the current noise spectral density (related to the... 

Correspondingly, according to the second FDT (20), the noise spectral density, which is the inverse Fourier transform of the random force correlation... 

For 8=1, the noise spectral density is a constant (white noise), at least in the angular frequency range co oo, the Langevin force F(t) is delta-correlated, and the Langevin equation is nonretarded. The white noise case corresponds to Ohmic friction. The cases 0 < 8 < 1 and 8 > 1 are known respectively as the sub-Ohmic and super-Ohmic models. Here we will assume that 0 < 8 < 2, for reasons to be developed below [28,49-51]. 

Applying the Wiener-Khintchine theorem, one obtains the velocity correlation function as the inverse Fourier transform of Cvv ( ), that is, in terms of the noise spectral density CFF([Pg.299]

Interestingly, due to the linearity of the generalized Langevin equation (22), the same effective temperature T,eff(( ) can consistently be used in the modified Nyquist formula linking the noise spectral density C/ /- ([Pg.313]

In the course of the measurement, the tip is positioned at a place of interest above the sample. Having obtained enou f-points to perform the time averaging, one may move to another space point in order to end up with the maps of 7 (u) and [u x,y) is the lateral coordinate along the surface]. Another important characteristic would be the current noise spectral density 5([Pg.47]

Noise spectral density (Eq. (2)) can be expressed through special functions. Since there is no problem in numerical calculation of S(co) using Eqs. (11) and (2), we will not set it out here. We present, however, simple results for the low-frequency noise. In the case of comparable and... 

We can observe that in this case, the cell measured noise emission spectral density is not flat versus frequency. Therefore we may consider that is composed of two components a constant noise spectral density due to the electrolyte itself an excess noise spectral density... 

The sensitivity of excess electrical noise to defects in device structure is the main reason to use the noise spectral density as a noise reUabihty indicator. The noise spectral density depends on stress and damage and varies among nominally identical devices. 

Our research was aimed to identify the sources of fluctuations in the dielectric layer prepared by anodic oxidation and to find the method for self-healing kinetics study. Charge carrier transport in thin isolating layer creates excess noise, which is the superposition of 1 /f and G-R noise. It has been observed, that samples with the same DC current have different noise spectral densities. We suppose that DC current is a sum of at least two independent current flow mechanisms, which have not the same noise intensity. 

The noise spectral density is l/f type in the frequency band 10 mHz to 300 Hz in normal and reverse operation mode. Noise spectral density is a quadratic function of the current, when the electric field strength in isolating layer is so low that avalanche process caimot occur. Measurement performed at very low frequency band 10 mHz to 1 Hz reveals that for some samples noise is l/f type, but it was observed some time instability, which is probably related to the self-healing process. 

After the self-healing event the noise spectral density decreases, but in some cases the burst noise appears. The change of noise voltage due to the self-healing is shown in Figs. 7 and 8. Here the l/f noise is changed into the superposition of the burst noise and l/f noise with lower noise spectral density (see Fig. 9 where curve A- corresponds to noise before self-healing event and B-after one). 

The most important sources of fluctuation in tan-taliun capacitors consist in regenerative micro breaks, fluctuation of polarization and mechanical strain. The frequency dependence of the noise spectral density in mHz region gives the information on slow irreversible processes of tantalum pentoxide crystallizations and oxide reduction. The self-healing process can improve... 

Figure 9. Noise spectral density before (A) and after (B) self-healing event.

Qualitative characterization of the excess noise is possible with the use of noise spectral density at given frequency (Sikula et al. 1994). In our investigation, the measurable quantity is an indicator of sample quality and reliability Cq given as... 

Where Su is noise spectral density,/ - frequency and U - apphed voltage. The lower value of Cq and its dispersion, the better is the technology. This hypothesis was proved by classical ageing methods. 

Figure 15. Noise spectral density of two 100 resistors. Curve 0 is the apparatus noise, curve 1 is noise spectral density of a low noise resistor and curve 2 is noise spectral density of a resistor with burst noise source.

The 1/f noise spectral density is usually carried out by means of a generalized Hooge s formula... 

Where 5/ is the current noise spectral density,/ is the frequency, N is the total number of carriers in the sample active region, I is the device DC current and a is an empirical constant, which is now extensively used to characterize the device structure perfectness. 

An analysis of RTS in this work quantitatively explains details of hole trapping processes in the tetrahedral-shaped recess quantum dot structure. Noise spectral density is given by superposition of 1/f noise and RTS pulses (Fig. 16) with the activation energy AEke= 190 meV for hole emission and AE),c= 260 meV for hole capture. RTS noise ampUtude has its maximum value at temperature range below 300 K when the quasi Fermi level coincides with the trap energy level. At temperature higher than 300 K the 1/f noise component is dominant and then parameter Cq given by (4) is used as quality and rehabihty indicator. 

The noise spectral density Su is superposition of g-r and 1/f noise as is shown in Fig. 18. For constant gate voltage and variable drain voltage it was foimd that 1/f noise spectral density decreases due to that the channel carrier concentration increases with temperature (Simoen et al. 1997). On the other hand, for constant gate voltage and constant drain current 1/f... 

Figure 18. The voltage noise spectral density vs. frequency for sample N51 at T = 298K and 260K.

In lasers, luminescent diodes, power diodes and solar cells it was found that in the low injection region the current noise spectral density is a quadratic function of the forward current. Typically, the excess current is a dominant current component in this region. The current noise spectral density vs. frequency for PN junction is shown in Fig. 19. Curve 1 denotes the current noise spectral density for the low injection range, curve 2 is the current noise spectral density for the... 

J. T. MIHALCZO and V. K. PARE, Feasibility of Reactivity Determination from Neutron Noise Spectral Density with Cf in the Initial Loading of Light-Water-Moderated Reactors, Trans. Am. Nucl. Soc., 28,799(1978). 

Measured input-noise spectral densities of VLSI nanoclamp and backgroimd in the nanopore sensing. 

This noise power spectral density expressed in Equation (1.5) and Equation (1.6) increases linearly with absolute temperature, and is independent of frequency. By solving Equation (1.6) for the temperature T, it is possible to determine it from the available noise spectral density. This can be extended to define a noise temperature for any source of white noise, even nonthermal noise, in order to allow convenient... 

Noise power density represents the average noise power over a 1-Hz bandwidth as a function of frequency. A companion quantity is noise spectral density denoted by e (f) with units given by volts/ hertz. 

The noise power density of 1 // noise has the form e (/) = K /f where Ky is a constant representing the extrapolated value of the noise spectral density at / = 1 Hz. The spectral density of l/f noise is Kyl f indicating that on a log-log plot the spectral density has a slope of—0.5 decades/decade. The rms value of 1 // noise, obtained from Eq. (7.141), is... 

The noise sources in the noise model for an op-amp are composed of a mixture of white and 1 // noise as shown for a voltage noise source in Fig. 7.98. At low frequencies, l/f noise dominates, and at high frequencies, white noise dominates. The boundary is called the corner frequency and is denoted as fey in Fig. 7.98. A similar plot appHes to the noise spectral density of current noise sources in the op-amp model. The corner frequency for a noise current source is denoted as f. ... 

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