Popcorn Noise Research Articles

Improved Superresolution Imaging Using Telegraph Noise in Organic Semiconductor Nanoparticles.

Small semiconductor structures often exhibit "telegraph noise". If the number of charge carriers is small, then spontaneous changes in the number of carriers can lead to abrupt switching between two or more discrete levels, leading to burst noise or popcorn noise in transistors. We have observed similar behavior in the fluorescence of organic semiconductor nanoparticles, where typical carrier populations are often less than ∼10 carriers per nanoparticle. Spontaneous changes in the number of charges results in abrupt switching between 2 or more fluorescence intensity levels, because the charges act as highly efficient fluorescence quenchers. The equilibrium number of charges is determined by competition between a photodriven ionization process and spontaneous recombination. Doping with redox-active molecules also affects the balance. Nanoparticles of the conjugated polymer PFBT doped with the fullerene derivative PCBM, rapidly establish a fluctuating steady-state population of tens of hole polaron charge carriers, sufficient to nearly completely suppress nanoparticle fluorescence. However, fluctuations in the number of charges lead to occasional bursts of fluorescence. This spontaneous photoswitching phenomenon can be exploited for superresolution imaging. The repeated, spontaneous generation of short, intense bursts of fluorescence photons results in a localization precision of ∼0.6 nm, about 4 times better than typical resolution obtained by localization of dye molecules.

A 2 $\mu\hbox{W}$ 100 nV/rtHz Chopper-Stabilized Instrumentation Amplifier for Chronic Measurement of Neural Field Potentials

This paper describes a prototype micropower instrumentation amplifier intended for chronic sensing of neural field potentials (NFPs). NFPs represent the ensemble activity of thousands of neurons and code-useful information for both normal activity and disease states. NFPs are small - of the order of tens of muV- and reside at low bandwidths that make them susceptible to excess noise. Therefore, to ensure the highest fidelity of signal measurement for diagnostic analysis, the amplifier is chopper-stabilized to eliminate 1/f and popcorn noise. The circuit was prototyped in an 0.8 mum CMOS process and consumes under 2.0 muW from a 1.8 V supply. A noise floor of 0.98 muVrms was achieved over a bandwidth from 0.05 to 100 Hz; the noise-efficiency factor of 4.6 is one of the lowest published to date. A flexible on-chip high-pass filter is used to suppress front-end electrode offsets while maintaining relevant physiological data. The monolithic architect and micropower low-noise low-supply operation could help enable applications ranging from neuroprosthetics to seizure monitors that require a small form factor and battery operation. Although the focus of this paper is on neurophysiological sensing, the circuit architecture can be applied generally to micropower sensor interfaces that benefit from chopper stabilization.

An Investigation of Row-Bar Level Quasi-Static Test for Perpendicular Recording

Popcorn noise is a large transient noise spike at the reader shortly after writing due to unstable domains in writer yoke. The popcorn noise was found to dependent on write frequency. It is firstly reported that the popcorn noise occurred by the write instability of shielded-single-pole head (SSPH) can be captured in row-bar level QST which is experimentally confirmed. Thus, a PMR head can be rejected by the row-bar level QST. In addition, the writing stress traced by the MR transfer curve can possibly accelerate the head degradation.

Stochastic Background from Coalescences of Neutron Star–Neutron Star Binaries

In this work, numerical simulations were used to investigate the gravitational stochastic background produced by coalescences of double neutron star systems occurring up to z ~ 5. The cosmic coalescence rate was derived from Monte Carlo methods using the probability distributions for massive binaries to form and for a coalescence to occur in a given redshift. A truly continuous background is produced by events located only beyond the critical redshift z* = 0.23. Events occurring in the redshift interval 0.027 < z < 0.23 give rise to a noise, while those closer than z = 0.027 produce a shot noise. The gravitational density parameter Ωgw for the continuous background reaches a maximum around 670 Hz with an amplitude of 1.1 × 10-9, while the popcorn noise has an amplitude about 1 order of magnitude higher and the maximum occurs around a frequency of 1.2 kHz. The signal is below the sensitivity of the first generation of detectors but could be detectable by the next generation of ground-based interferometers. Correlating two coincident advanced LIGO detectors or two EGO interferometers, the expected S/N are respectively 0.5 and 10.

Write frequency dependence of popcorn noise in GMR heads

Popcorn noise of integrated inductive write/GMR read heads was characterized at various write currents and frequencies. The popcorn noise count tends to increase with write current and peaks at a certain frequency. This was attributed to heating-cooling cycles of heads induced by the write current, which rolls off with frequency. In fact, it was observed that write current heating peaks around the same frequency. The heating is caused by Joule heating of writer coils and eddy current loss of the writer core. A larger popcorn count was observed if the heat diffusion path is restrained, for example, by unloading heads from the media surface. The clock frequency at which the popcorn noise peaks is higher when tested with a pseudo-random write pattern instead of a single frequency pattern. Potential impact of high data rate and write current rise time of preamplifiers is discussed.

Dynamic domain instability and popcorn noise in thin-film heads

The effects of dynamic domain instability on popcorn noise probabilities were studied by correlating the measured popcorn noise probabilities with the instantaneous observations of dynamic domain states of thin-film heads during and after writing. Heads with large peak popcorn noise probabilities at intermediate values of write current amplitude were observed to exhibit asymmetric domain patterns and occasional popping wall motion in the yoke structure during writing. The occurrences of dynamic domain instability were imaged by comparing many instantaneous domain patterns at 10 μs after a specific write current excitation. Delayed-relaxation Barkhausen wall jumps near the backgap closure were observed occasionally in several noisy heads. Quantitative correlation between the probabilities of popcorn noise and dynamic domain instability was also obtained in a very noisy head. Dynamic domain instabilities in the yoke are thus responsible for the peak popcorn noise probabilities in thin-film heads.

Inductance fluctuation, domain instability and popcorn noise in thin film heads

The mechanisms of popcorn noise in thin film heads were studied by correlating the inductance fluctuations under DC bias current, domain instabilities after write and popcorn noise probabilities. Inductance fluctuations of heads were obtained by calculating the standard deviations of the inductance values measured from 20 traces by a HP network analyzer. Instantaneous domain patterns during and after write as well as popcorn noise probabilities of heads were observed by a 0.5-nsec exposure time wide-field Kerr effect microscope and a Barkhausen noise tester, respectively. A strong correlation was found among inductance fluctuations, domain instabilities and popcorn noise probabilities in a noisy head. This relationship was further confirmed by the quantitative correlation between the peak popcorn noise probabilities and peak inductance fluctuations of 12 different heads. Therefore, by measuring the inductance fluctuations of thin film heads under DC bias current, one can infer their susceptibilities to Barkhausen wall jumps, and thus popcorn noise probabilities. >

High density recording FeTaN laminated hard disk heads

Laminated hard disk heads with FeTaN films, which have high saturation magnetic flux density of 16 kG, have been developed for high density magnetic recording. Here, read/write characteristics for FeTaN heads are evaluated and compared with the value for Sendust laminated heads. The FeTaN heads have better overwrite characteristics by 10 dB than Sendust heads. Even for 2400 Oe high coercivity media, the overwrite value is -32 dB. Output voltage for the FeTaN head is at least 1.2 times higher than that for a Sendust head. Popcorn noise and wiggle noise are low enough for practical use. FeTaN heads are shown to have a great potential to achieve high areal density recording. >

A study of popcorn noise for thin film heads

The magnetic domains of the yoke and heat generated in coils were investigated as possible sources of popcorn noise. It was found that the movement of the magnetic walls was the primary factor affecting the noise. When the magnetic walls were hard to move as the number of the magnetic domains increased the popcorn noise was difficult to observe. The magnetic domain configuration of the yoke was optimized by changing the shape and Fe-Ni composition of the yoke. The appearance probability of popcorn noise decreased by 60% as the Fe component was changed from 18.6 wt.% to 17.6 wt.%. The appearance probability of popcorn noise decreased by 70% as the yoke width was changed from 170 mu m to 80 mu m. >

Computerized Analysis of Burst Noise in Thick Film Resistors

A burst noise (popcorn noise) spectral measurement technique based on digital power spectrum estimation is presented. Application of this technique to thick film resistor burst noise is discussed. Several cases of thick film resistor burst noise are presented and analyzed.

Sidewall penetration of dislocations in ion-implanted bipolar transistors

Phosphorus-doped emitters have been formed by either conventional diffusion or implantation, anneal, and drive-in processes. Transmission electron microscopy and measurements of transistor characteristics were made to evaluate the two processes. Comparison of structures with similar dislocation densities indicated that the dislocations in the implanted structures penetrated the emitter-base sidewall, whereas the dislocations in the diffused structure were confined to the emitter region. The transistor with extended dislocations exhibited high leakage current and excess popcorn noise generating.

Comments on the emitter-current density dependence of popcorn noise frequency

It has been found that the power spectrum of popcorn noise in integrated-circuit transistors can extend well into the audio-frequency range even at low emitter-current densities.

Reduction of popcorn noise in integrated circuits

Popcorn (burst) noise continues to deteriorate the operation of linear IC devices. Reduction of popcorn noise by a few simple modifications in the manufacturing process is reported in this paper. Annealing in an HC1 atmosphere to getter metal impurities and slow pulling after emitter deposition to diminish stress-induced junction defects appear to reduce the popcorn noise significantly.

The effect of emitter-current density on popcorn noise in transistors

It was found experimentally that the pulsewidth of popcorn noise has a dependence on the emitter current density. Experimental results show that, when a transistor having popcorn noise is operated at the emitter current density less than about 1.56 × 10-1A/cm2, the popcorn-noise characteristic is scarcely in the frequency range higher than 15 Hz, well below the audible frequency limit.

Popcorn noise and generation-recombination noise observed in ion-implanted silicon resistors

Experimental results show that, for low currents, the generation-recombination noise component increases with current, and, at higher currents, it decreases inversely with current. For currents greater than a certain value, a generation-recombination noise component is scarcely observed.

Discussion of various views on popcorn noise

Conflicting ideas regarding popcorn (burst) noise are compared. It is shown that it is premature to use a single model or claim for a unique representation and explanation.

An investigation into the origin and nature of "Popcorn noise"

The phenomenon of popcorn noise is discussed and shown to exist in integrated wideband amplifiers when an input transistor of the amplifier exhibits a negative resistance region in the reverse-biased collector-base characteristic. A correlation is drawn between popcorn noise and microplasma noise.