Flicker Noise

We demonstrate spin torque induced auto-oscillation in MgO-based magnetic tunnel junctions. At the generation threshold, we observe a strong line narrowing down to 6 MHz at 300K and a dramatic increase in oscillator power, yielding spectrally pure oscillations free of flicker noise. Setting the synthetic antiferromagnet into autooscillation requires the same current polarity as the one needed to switch the free layer magnetization. The induced auto-oscillations are observed even at zero applied field, which is believed to be the acoustic mode of the synthetic antiferromagnet. While the phase coherence of the auto-oscillation is of the order of microseconds, the power autocorrelation time is of the order of milliseconds and can be strongly influenced by the free layer dynamics.

We show that certain extended dissipative dynamical systems naturally evolve into a critical state, with no characteristic time or length scales. The temporal "fingerprint" of the self-organized critical state is the presence of flicker noise or 1/f noise; its spatial signature is the emergence of scaleinvariant (fractal) structure.

We investigate hot-carrier degradation of the 1 -noise behavior of n-and p-MOS transistors under typical bias conditions for analog and RF operation. The mechanisms responsible for the degradation and a model are discussed for both n-and p-MOS devices. A method for lifetime prediction concerning 1 -noise degradation is presented and consequences for reliability assurance by measures of circuit design are drawn. Index Terms-1 -noise, analog, flicker noise, hot carrier, MOS, MOSFET, noise, RF.

Transistor mismatch data and analysis from poly/ SiON and high-k/metal-gate (HKMG) bulk CMOS technologies are presented. It is found that the traditional mismatch figure of merit from the Pelgrom plot (A VT ) continuously scales down as technology advances. Furthermore, the A VT values for both nFET and pFET in the HKMG technology are significantly reduced from poly/SiON technologies. By normalizing the mismatch data against electrical oxide thickness (T INV ), threshold voltage (V TH ), and effective work function, a direct comparison of the mismatch data from various technologies is made. The differences in nFET and pFET mismatch behaviors in both poly/SiON and HKMG technologies are discussed in detail. Correlation between transistor V TH mismatch and flicker noise variation is observed in both poly/SiON and HKMG technologies. Finally, it is quantitatively demonstrated that effective work function variation does not generate significant V TH variability in the present HKMG technology. Index Terms-Bulk CMOS technology, effective work function, flicker noise variation, high-k/metal gate (HKMG), Pelgrom mismatch slope (A VT ), poly/SiON, random dopant fluctuation (RDF), Takeuchi normalization method, threshold voltage (V TH ) variability.

This paper describes a new structure for a three stage low noise operational amplifier in a 0.18 CMOS process. Design strategies are discussed for minimizing noise and increasing gain. Nested miller compensation used for three stage operational amplifier. The simulation results show that the Op-Amp has been improved for a high-gain (128.5dB), low-noise and UGBW (794MHz). MATLAB and Hspice software's used for simulation.

A single port llf model is examined of a crystal oscillator combined with a resonator and an equivalent negative resistance of amplifier. Intrinsic l/f flicker fluctuations of resonator and amplifier amplitude and phase are converted to the oscillator amplitude and phase, and the proper transformation coefficients are applied. An analysis of the oscillator phase power spectral density is provided in detail for the particular case of a resonator excited in oscillator at various frequencies. Conformity with the Leeson's model is shown.'

Abstract, A CMOS passive mixer is designed to mitigate the critical flicker noise problem that is frequently encountered in constituting direct-conversion receivers. With a unique single-bal-anced passive mixer design, the resulted direct-conversion receiver achieves an ultralow flicker-noise corner of 45 kHz, with 6 dB more gain and much lower power and area consumption than the double-balanced counterpart. CMOS switches with

—We present a fully integrated 7nm CMOS platform featuring a 3 rd generation finFET architecture, SAQP for fin formation, and SADP for BEOL metallization. This technology reflects an improvement of 2.8X routed logic density and >40% performance over the 14nm reference technology described in [1-3]. A full range of Vts is enabled on-chip through a unique multi-workfunction process. This enables both excellent low voltage SRAM response and highly scaled memory area simultaneously. The HD 6-T bitcell size is 0.0269um 2. This 7nm technology is fully enabled by immersion lithography and advanced optical patterning techniques (like SAQP and SADP). However, the technology platform is also designed to leverage EUV insertion for specific multi-patterned (MP) levels for cycle time benefit and manufacturing efficiency. A complete set of foundation and complex IP is available in this advanced CMOS platform to enable both High Performance Compute (HPC) and mobile applications.

In this paper, a low power, low flicker noise and high IIP3 I/Q mixer for 76-108MHz EURO/US/Korea/Japan FM radio receiver applications is presented. The proposed mixer includes a transconductance (Gm) stage, a current mode passive switching stage driven by a 25% duty cycle LO, a transimpedance amplifier (TIA), and a 25% duty cycle LO generator. Simulation results show a 9.2dB DSB noise figure at 50kHz, 13dBm IIP3, and 23dB voltage gain, respectively, while drawing only 800uA including a LO generator from a 1.2-V supply in a standard 65nm CMOS technology.

Low frequency noise measurements are among the most sensitive tools for the investigation of the quality and of the reliability of semiconductor devices. The sensitivity that can be obtained depends on the background noise of the low noise preamplifier coupled to the device under test (DUT) that, at very low frequencies, is dominated by flicker noise. The low frequency noise produced by the DUT, on the other end, is very often the most interesting signal to be detected and analyzed. In this work we propose a very simple topology for the realization of a general purpose low noise preamplifier whose noise performances, at very low frequencies (below 10 Hz), are significantly better than those that can be obtained by the most popular commercial instrumentation. Indeed, a gain of 80 dB with a pass band extending from a few tens of mHz up to a few kHz with an equivalent input voltage noise as low as 14 nV/square root(Hz) (100 mHz), 1.4 nV/square root(Hz) (1 Hz), 1.0 nV/square root(Hz) (10 Hz), and 0.8 nV/square root(Hz) (1 kHz) are consistently obtained by using quite standard electronic components and with no need for trimming and/or calibration steps. Moreover, the junction field-effect transistor input stage of the amplifier is characterized by an equivalent input current noise below 4 fA/square root(Hz) in the entire bandwidth, resulting in negligible background noise degradation for DUT impedances in excess of 100 kohms.

As the scaling limit of silicon CMOS technology draws to an end, there is a critical need for novel materials and devices to drive the next generation of information processing. Graphene is one such promising candidate. Although graphene features exceptional intrinsic carrier mobility, thermal conductivity, and physical endurance, this two-dimensional material is quite sensitive to its environment as a result of its high surface-to-volume ratio. Variability effects become dominant and result in unreliable graphene devices. In order to realize high signal-to-noise ratio graphene devices for high-speed carbon-electronics, it is essential to investigate and minimize these variability
effects.

In this thesis, I present the preparation, design, and fabrication methods of single-layer and bilayer graphene sheet and graphene nanoribbon devices. Furthermore, I relate how these methods can contribute to the variability effects in graphene and graphene nanoribbons (GNR) devices while mentioning critical steps taken to minimize their influence. In order to understand how feasible graphene and GNR are for electronic devices, I investigate their device properties via electrical transport measurement and study their low-frequency (1/f) noise behaviors as a measure of how sensitive graphene and GNR are to their surroundings (e.g. surface traps near the graphene/SiO2 interface). Interestingly, graphene is shown to exhibit a noise behavior quite opposite to conventional semiconductor electronic materials – a noise minimum occurs when it is most resistive at its Dirac point. We also find that GNR devices show a direct correlation between the conductance fluctuations (noise) and the density-of-states of GNR. These results promote noise-metrology as a tool which can be used to probe the underlying band structure of quantum nanostructures.

This paper contains few interrelated parts. The short version of new quantum Hierarchic theory, general for solids and liquids, created by the author is presented. Condensed matter in this theory is considered as a system of 3D standing waves (collective excitations) of different nature: thermal de Broglie waves (waves B), IR photons, related to intermolecular oscillations and thermal phonons. Theory is verified by computer simulations on examples of pure water and ice, using special computer program, yielding more, than 300 parameters. Theory based idea of new optoacoustic device: Comprehensive Analyzer of Matter Properties (CAMP), its various configurations and applications are presented. The full version of this paper is located at http://arXiv.org/abs/physics/0102086. Good correlation between simulated parameters of water and proteins dynamic structure points to crucial role of water in biopolymers evolution. It is shown, that multi-fractional model of interfacial water structure, proposed by the author, could be responsible for some of morphogenetic field properties. Computer simulations point, that coherent water clusters could be in state of mesoscopic molecular Bose condensation (mBC). The coherent IR radiation of such kind of enlarged clusters is supposed to be responsible for exchange interaction between distant microtubules of different neurons, stimulating [gel-sol] transitions in neurons bodies and synaptic reorganization. It is a part of elementary act of consciousness (quantum Mind) proposed. Unified model of Bivacuum, corpuscle [C] -wave [W] duality, electromagnetic and gravitational fields has been developed. Bivacuum is considered as the infinitive continuum, formed by the mass, electric and magnetic dipoles (Bivacuum fermions). Sub-elementary particles/antiparticles are the result of stable Bivacuum fermions symmetry shift, determined by resonant energy exchange interaction with Bivacuum. The triplets of sub-elementray particles and sub-elementary antiparticles form the elementary particles. The [C -W] pulsation of sub-elementary particles are accompanied by quasi-reversible emission -absorption of cumulative virtual clouds (CVC), formed by subquantum particles. The irreversible parts of CVC energy, deriving from zero-point translational (longitudinal and transversal) vibrations, are responsible for electromagnetic and gravitational fields creation. The massless nonlocal wave-guide (channel) between Sender [S] and Receiver [R], formed by virtual spin waves (VirSW) of Bivacuum with properties of Nambu-Goldstone collective modes, are excited by the angular moment (spin) of reversible part of CVC energy (rotational), responsible for the rest mass of particles. The internal magnetic field and refraction index inside the virtual wave-guide are bigger, than the external ones, providing spatially selective exchange of virtual photons (

Voltage supply scaling in CMOS processes requires lower inductance and higher capacitance in conventional LC oscillators. Forcing several LC oscillators to run in phase is a valuable means of achieving the wanted phase noise with practical values of inductances and capacitances. However, in-phase oscillator arrays suffer from the up-conversion of transistors' flicker noise, in the presence of oscillator mismatches. A multitank oscillator topology is proposed, which has superior tolerance to mismatches and removes this mechanism of noise degradation. In order to assess such topology, an 802.11 a-compliant VCO with four coupled oscillators has been designed in a 0.13-mum CMOS technology. A phase noise better than -120 dBc/Hz at 1-MHz offset has been achieved along the 4.7-5.9-GHz tuning range

Voltage supply scaling in CMOS processes requires lower inductance and higher capacitance in conventional LC oscillators. Forcing several LC oscillators to run in phase is a valuable means of achieving the wanted phase noise with practical values of inductances and capacitances. However, in-phase oscillator arrays suffer from the up-conversion of transistors' flicker noise, in the presence of oscillator mismatches. A multitank oscillator topology is proposed, which has superior tolerance to mismatches and removes this mechanism of noise degradation. In order to assess such topology, an 802.11 a-compliant VCO with four coupled oscillators has been designed in a 0.13-m CMOS technology. A phase noise better than 120 dBc/Hz at 1-MHz offset has been achieved along the 4.7-5.9-GHz tuning range.

This paper presents a physical derivation of phase noise in source-coupled-logic frequency dividers. This analysis takes into account both white and flicker noise sources and is verified on two 32/33 dual-modulus prescalers integrated in a 0.35-m CMOS process. Design techniques for high-speed and low-noise operation are provided. The two integrated prescalers are identical apart from a synchronizing flip-flop at the output of one of them. The measured phase spectra are in good agreement with the estimates and demonstrate that the final synchronization allows a better trade-off between noise and power consumption. The maximum operating frequency is 3 GHz, the power consumption is 27 mW and the phase noise floor is 163 dBc/Hz referred to the 78-MHz output.

The noise figure of an RF CMOS mixer is strongly affected by flicker noise. The noise figure can be improved using pMOS switch circuits, which insert current at the on/off crossing instants of the local oscillator switch stage because the circuits reduce the flicker noise injection. When it is applied to a conventional Gilbert mixer, the injection efficiency and linearity are degraded by the nonlinear parasitic capacitances of the pMOS switch circuits and the leakage through the parasitic path. We propose the pMOS switch circuits with an inductor, which tunes out the parasitic components at 2 and closes out the leakage path. The mixer fabricated in 0.13-m CMOS at 2.4-GHz center frequency has provided improved characteristics for linearity and noise figure.

In the literature, a Folded Switch Mixer (FSM) which uses self-bias current reuse technique at the transconductance stage is proposed and implemented in TSMC 90 nm CMOS process, for achieving high Conversion Gain (CG), good linearity and low Noise Figure (NF). In order to increase the CG and reduce the NF of FSM further, a Dynamic Current Injection FSM (CI-FSM) is proposed in this paper. For the purpose of comparison, FSM and CI-FSM are implemented in UMC 180 nm CMOS process and studied through simulation at 2.4GHz. From the study, it is found that the CG of CI-FSM is higher by 2dB and NF of CI-FSM approximately lower by 1.0dB compared to that of the FSM. But CI-FSM has maintain near same linearity (4dBm) compared to FSM (6dBm) at the cost of increase in area.

The oscillator architecture is proposed to reduce the close-in phase noise as well as power consumption. The proposed Colpitts oscillator removes the current source which is the main source of the 1/f noise conversion. The removal of the current source is compensated by using the transformer and cross-coupled capacitors. The 2-GHz film bulk acoustic resonator (FBAR) is used for the high Q frequency selective elements in the oscillator design. According to measurement results, this FBAR-based oscillator shows ≥ 10 dB reduction in close-in phase noise. Specifically, 12-dB lower phase noise is achieved at 100 Hz offset frequency. Measured power consumption is 350 uW, which is almost half of the conventional Colpitts oscillator using same FBAR device.

The effect of device noise on oscillator phase noise in a close vicinity of average oscillator frequency is analyzed. We show that for 1/f noise, the line shape of a free-running oscillator changes from power to approximately Gaussian function very close to the oscillator frequency. The Gaussian regime occurs when the relationship between device noise and oscillator spectrum is strongly nonlinear. As this relationship approaches linear dependence at higher frequency deviation, there occurs a smooth crossover from Gaussian to well-known power line shape. The commonly used power extrapolation turns out to significantly underestimate phase noise in a part of the near-carrier frequency range.

A noise analysis of bipolar harmonic mixers (BHM) used for direct-conversion receivers is presented in this paper. Analytical and simulated results for the transfer function of the mixer are presented. Simple analytical expressions describing noise contribution from all sources are derived. Estimation of flicker noise quite agrees with harmonic-balance simulation results. Based on the derived expressions, total time average noise power spectral density (PSD) at the output is compared with simulation results. For the recommended regions of operation, error is less than 20%. The overall BHM noise figure (NF) is calculated and optimized based on a simple extracted formula. Errors introduced by analysis remain within a 1.5-dB margin with respect to simulation results. The validity of analysis for high frequencies is justified. The effect of flicker noise coefficient on the overall mixer NF is compared for different available processes.

The success of organic circuits depends on the implementation of novel fabrication techniques, and circuit designs which utilize organic semiconductor characteristics. We present DC, transient, and noise measurements of discrete organic FETs, and use these characteristics in SPICE simulations of complementary MOS circuits ranging in complexity from inverters through shift registers. Source/drain contacts are fabricated using electroless Ni/Au electrode deposition, a method well suited for incorporation with other fabrication techniques such as screen printing and microcontact printing.

We show that dynamical systems with spatial degrees of freedom naturally evolve into a self-organized critical point. Flicker noise, or 1/f noise, can be identified with the dynamics of the critical state. This picture also yields insight into the origin of fractal objects.

The possibility in principle of extending metrological concepts to the characteristics of complex objects, the primary information about the state or structure of which is presented in the form of complex chaotic dependences and cannot be expressed using standard metrological images such as directly measured time and length and other dimensional values, is shown. To correctly characterize the dynamic state of such complex objects, including states of objects during nonstationary evolution, or the special features of struc tures formed under the conditions of external actions of various intensities, it is necessary, first, to introduce autocorrelation dependences averaged over time or spatial intervals on the basis of measured dynamic vari ables and, next, to use these dependences to find sets of information parameters, which can be presented as metrological characteristics of the dynamic state under study or spatial image to be analyzed. The phenome nological basis of the corresponding analysis is provided by flicker noise spectroscopy with its possibilities of developing procedures and algorithms that can be used to obtain metrological characteristics over various fre quency (time and spatial) ranges of the signals analyzed. This is the basis on which unity of metrological char acteristic measurements with a determined uncertainty (error) in measurements can be achieved, standards and reference samples of fluctuation metrology can be created, and methods for the transfer of standard parameters from standards to reference samples and then to working measurement instruments can be devel oped. This opens up the possibility for solving many practical problems of microelectronics, energetics, nanoindustry, chemical technology, which include standardization of the state of complex systems and arti cles of various functional purposes, and the quality of products created.

By measuring the frequency-noise power spectral density of a cryogenically-cooled mid-infrared quantum cascade laser, we investigate the different contributions to the noise spectrum and identify the main differences with respect to standard bipolar semiconductor devices. In particular, the existence of a thermal cut-off on the 1/ f noise allows to identify the current fluctuations through the heterostructure as the physical mechanism, intrinsic to the device, at the basis of the measured flicker noise. This result, marking the difference with bipolar semiconductor devices, is confirmed analyzing the laser frequency response to a modulation of the driving current.

A study of the noise performance of gate overlapped polycrystalline silicon thin-film transistors (TFTs) is presented. Low-frequency noise measurements were carried out on n-and p-type samples fabricated by excimer laser crystallization. It is shown that the carrier number fluctuation model applies not only to n-type but also to p-type devices. The density of oxide traps was extracted from the noise measurements and was of the order of 10 18 -10 19 eV 1 cm 3 .

In the last few years cellular market well exceeded 1.3B cellular mobile devices shipped per year. The ongoing economic-driven shrink in technology towards nanoscale CMOS enables increased functionality in even smaller silicon area, however, technology effects including process variation, variability, temperature effects, flicker noise etc. put stringent challenges on the design and have significant impact on the production yield. Due to the huge volume yield, testing and Automated Test Equipment (ATE) have become a major cost factor in RF production. At the same time integration level and complexity of RF transceivers and SoCs have increased due to huge diversity of mobile communication standards ranging from 2G/3G to 4G, WLAN, BT, and GPS. RF devices are no longer purely RF devices. They integrate RF, analog and digital functions, all working together enabling the device to test and calibrate functions autonomously. This paper summarizes the key developments and trends in RF-BIST, with particular attention to improvements in testing and calibration of PLL loop-gain, second order modudulation, and I/Q impairments.

By measuring the frequency-noise power spectral density of a cryogenically-cooled mid-infrared quantum cascade laser, we investigate the different contributions to the noise spectrum and identify the main differences with respect to standard bipolar semiconductor devices. In particular, the existence of a thermal cut-off on the 1/ f noise allows to identify the current fluctuations through the heterostructure as the physical mechanism, intrinsic to the device, at the basis of the measured flicker noise. This result, marking the difference with bipolar semiconductor devices, is confirmed analyzing the laser frequency response to a modulation of the driving current.

A complete 65 nm CMOS platform, called LP/GP Mix, has been developed employing thick oxide transistor (IO), Low Power (LP) and General Purpose (GP) devices on the same chip. Dedicated to wireless multi-media and consumer applications, this new triple gate oxide platform is low cost (+1mask only) and saves over 35% of dynamic power with the use of the low operating voltage GP. The LP/ GP mix shows competitive digital performance with a ring oscillator (FO = 1) speed equal to 7 ps per stage (GP) and 6T-SRAM static power lower than 10 pA/cell (LP). Compatible with mixed-signal design requirements, transistors show high voltage gain, low mismatch factor and low flicker noise. Moreover, to address mobile phone demands, excellent RF performance has been achieved with F T = 160 GHz for LP and 280 GHz for GP nMOS transistors.

Many dynamical systems from different areas of knowledge can be studied within the theoretical framework of time series, where the system can be considered as a black box, that only needs to be ``listened'' to. In this framework, non-correlated series (white noise) and strongly correlated series (brownian noise or periodic series) constitute two extremes. Certain dynamical systems auto-organize in a critical state that is characterized by 1/f or flicker noise. The family of fβ noises (β<=0) is fractal because fragments of the series are statistically identical to the original time series. 1/f noise (β = -1) is critical because it maximizes important complexity-related quantities as memory, information content, efficiency and fractality. 1/f noise has been observed in classical systems, but also in quantum systems, and could possibly offer a unifying bridge of understanding between the macroscopic and the quantum world. In the present article, we will discuss some examples from both worlds.

In this paper, the short channel effects in buried and surface channel pMOSFETs are studied. The effective channel length, threshold voltage, source-drain series resistance, carrier mobility in various temperature ranges and the draininduced-barrier-lowering effect are investigated. Hot carrier degradation is performed in order to extrapolate the device lifetimes and the maximum drain bias that can be applied. Low frequency noise measurements are also carried out in order to evaluate the impact of the gate doping type on the device noise performance. Ó

We show that certain extended dissipative dynamical systems naturally evolve into a critical state, with no characteristic time or length scales. The temporal "fingerprint" of the self-organized critical state is the presence of flicker noise or 1/f noise; its spatial signature is the emergence of scaleinvariant (fractal) structure.

1/f noise has been investigated on the drain to source voltage of deep sub-micron p-channel MOSFETs, with 5 μm channel width and 0.32–1.2 μm varying lengths. The MOSFETs were fabricated using 0.18 μm medium doped drain technology. The measurements were performed in strong inversion and linear operation region at room temperature. Noise parameters for BSIM3 simulation were extracted from the

The demand of voltage-controlled oscillators (VCOs) with a broad tuning range can lead to unacceptable degradation of the 1/f 3 phase-noise component if traditional voltage-biased topologies are implemented. In this paper, a novel VCO architecture is proposed, where a segmented transconductor tailors the negative gm depending on the operating range to ensure that flicker-noise up-conversion remains minimal. The implemented oscillator covers both 4G and WiMAX 2.5-GHz operation modes and achieves a 10-dB reduction of the 1/f 3 phase noise without impairing the 1/f 2 phase-noise performance.

Noise measurements of the 1 noise in PMOS and NMOS transistors for analog applications are reported under wide bias conditions ranging from subthreshold to saturation. Two "low noise" CMOS processes of 2 m and 0.5 m technologies are compared and it is found that the more advanced process, with 0.5 m technology, exhibits significantly reduced 1 noise, due to optimized processing. The input referred noise and the power spectral density (PSD) of the drain current 1 noise are modeled in saturation as well as in subthreshold and are compared with the common empirical approaches such as the SPICE models. The results of this study are useful to the design and modeling of 1 noise of CMOS analog circuits.

We have used up to 12 years of data to assess DORIS performance for geodynamics applications. We first examine the noise characteristics of the DORIS time-series of weekly station coordinates to derive realistic estimates of velocity uncertainties. We find that a combination of white and flicker noise best explains the DORIS time-series noise characteristics. Second, weekly solutions produced by the Institut Géographique National/Jet Propulsion Laboratory (IGN/JPL) DORIS Analysis Centre are combined to derive a global velocity field. This solution is combined with two independent GPS solutions, including 11 sites on Nubia and 5 on the Somalia plate. The combination indicates that DORIS horizontal velocities have an average accuracy of 3 mm/year, with best-determined sites having velocity accuracy better than 1 mm/year (one-sigma levels). Using our combined velocity field, we derive an updated plate kinematics model with a focus on the Nubia–Somalia area. Including DORIS data improves the precision of the angular velocity vector for Nubia by 15%. Our proposed model provides robust bounds on the maximum opening rates along the East African Rift (4.7–6.7 mm/year). It indicates opening rates 15 and 7% slower than values predicted by NUVEL-1A for the southern Atlantic Ocean and Indian Ocean, respectively. These differences are likely to arise from the fact that NUVEL-1A considered Africa as a single non-deforming plate, while here we use a more refined approach.

Harmonic content modulation of the oscillator output voltage waveform can contribute to flicker noise up-conversion in LC-tuned oscillators. The paper reports a quantitative analysis of the effect in Van der Pol oscillators using the framework of the impulse sensitivity function (ISF). It is shown that most of the up-conversion efficiency results from the first harmonic of the ISF, which is not perfectly in quadrature to the output voltage waveform, and from the first harmonic of the transistor current, which is slightly lagging the voltage waveform. A closed-form expression of phase noise in voltage-limited LC-tuned oscillator is derived that is in good agreement with circuit simulations. The paper also shows that the values of both phase shifts are determined by the non-linearity of the active element and are linked to the relevant oscillator parameters, i.e., excess gain and tank quality factor.

This paper presents a physical derivation of phase noise in source-coupled-logic frequency dividers. This analysis takes into account both white and flicker noise sources and is verified on two 32/33 dual-modulus prescalers integrated in a 0.35-m CMOS process. Design techniques for high-speed and low-noise operation are provided. The two integrated prescalers are identical apart from a synchronizing flip-flop at the output of one of them. The measured phase spectra are in good agreement with the estimates and demonstrate that the final synchronization allows a better trade-off between noise and power consumption. The maximum operating frequency is 3 GHz, the power consumption is 27 mW and the phase noise floor is 163 dBc/Hz referred to the 78-MHz output.

With the growing efforts in isolating solid-state qubits from external decoherence sources, the material-inherent sources of noise start to play crucial role. One representative example is electron traps in the device material or substrate. Electrons can tunnel or hop between a charged and an empty trap, or between a trap and a gate electrode. A single trap typically produces telegraph noise and can hence be modeled as a bistable fluctuator. Since the distribution of hopping rates is exponentially broad, many traps produce flicker-noise with spectrum close to 1/f. Here we develop a theory of decoherence of a qubit in the environment consisting of two-state fluctuators, which experience transitions between their states induced by interaction with thermal bath. Due to interaction with the qubit the fluctuators produce 1/f-noise in the qubit's eigenfrequency. We calculate the results of qubit manipulations - free induction and echo signals - in such environment. The main problem is that in many important cases the relevant random process is both non-Markovian and non-Gaussian. Consequently the results in general cannot be represented by pair correlation function of the qubit eigenfrequency fluctuations. Our calculations are based on analysis of the density matrix of the qubit using methods developed for stochastic differential equations. The proper generating functional is then averaged over different fluctuators using the so-called Holtsmark procedure. The analytical results are compared with simulations allowing checking accuracy of the averaging procedure and evaluating mesoscopic fluctuations. The results allow understanding some observed features of the echo decay in Josephson qubits.

The development of an integrated amplifier intended to record electrical signals from extracellular peripheral nerves, using cuff electrodes, is presented. In order to minimize the flicker noise generated by the CMOS circuitry, a chopper full differential amplifier is implemented. The amplifier has a gain of 74 dB, a bandwidth of 3 kHz and a power dissipation of 1.3 mWatts, with 5 V power supply. Equivalent inputreferred noise level of 6.6 nV/(Hz) 0.5 has been achieved, obtaining a noise efficiency factor of 5.3, which is clearly competitive, compared with other developed recording amplifiers reported in the literature. The amplifier has been fabricated with a fully CMOS 0.7 m technology (one poly, two metals, self aligned twinwell CMOS process) and the active area is 2.7 mm 2 . In vivo nerve recordings are provided to demonstrate the feasibility of the amplifier.