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Based upon the experimental results of the two CFOA-based fully-uncoupled sinusoidal oscillators proposed earlier by Bhaskar-Gupta-Senani-Singh, recently Abuelma’atti and Khalifa issued a caution that the classification of this class of oscillators providing independent control of condition of oscillation (CO) and frequency of oscillation (FO) through separate elements, as fully-uncoupled , does not appear to be correct. In this communication, we present the results of a recheck of the experimental data of Abuelma’atti and Khalifa and show that their experimental results are not repeatable and in most of the cases , the oscillations do not even exist and hence, the measurement data as given by them is misleading. Furthermore, it is shown that the measured oscillation frequencies, as shown by Abuelma’atti and Khalifa in four tables, do not tally with those calculated from their own formula as well as the experimental results taken by us. This communication thus, refutes the claims made in the quoted paper of Abuelma’atti and Khalifa published in this journal earlier. [ABSTRACT FROM AUTHOR]

In this paper, broadly tunable dual-mode lasing system is presented and demonstrated based on single-mode Fabry-Pérot laser diode subject to the feedback of one side mode amplified by an erbium-doped fiber amplifier in the external feedback cavity. The spacing between two resonance modes in output lasing spectrum is broadly tuned by introducing differently amplified side mode into the single-mode laser via the external cavity consisted of amplifier, filter, and polarization controller so that two difference frequencies of 1 THz and 0.6 THz are given to display the tunable behavior of dual-mode emission in this work. Therefore, under an external injection mode into the laser condition, the power dependent injection locking and optical bistability of generated dual-mode emission are discussed in detail. At different wavelength detunings, the emitted two resonance modes including the dominant and feedback modes are switched to on- or off-state by selecting proper high-low power level of the external injection mode. As a consequence, the maximum value of achieved dual-mode on-off ratio is as high as up to 45 dB. [ABSTRACT FROM AUTHOR]

A new concept of a Charge Sensitive Amplifier without a high-value resistor in the feedback loop is presented. Basic spectroscopic parameters of the amplifier coupled to a coaxial High Purity Germanium detector (HPGe) are discussed. The amplifier signal input is realized with an n-channel J-FET transistor. The feedback capacitor is discharged continuously by the second, forward biased n-channel J-FET, driven by an RC low–pass filter. Both the analog—with a standard spectroscopy amplifier and a multi-channel analyzer—and the digital—by applying a Flash Analog to Digital Converter—signal readouts were tested. The achieved resolution in the analog and the digital readouts was 0.17% and 0.21%, respectively, at the Full Width at Half Maximum of the registered 60 Co 1332.5 keV gamma line. [ABSTRACT FROM AUTHOR]

The paper presents an analysis of problems associated with the area and power reduction of readout circuits used in multichannel neurobiology experiments, in relation to noise minimization. The noise limits of a single channel considered as a function of the silicon occupation and power consumption are analyzed for an amplifier working with capacitive feedback. The paper also presents an efficient method of noise minimization in multichannel recording systems used in neurobiology experiments, when the power budget and silicon area per single recording channel are strictly limited. The proposed idea was verified in an eight-channel prototype integrated circuit fabricated in CMOS 180 nm process. The prototype IC measurements show that with the use of the proposed method, one can decrease the recording channels’ noise two times with the existing dedicated power and area budget. [ABSTRACT FROM AUTHOR]

Summary Scattering of light by disordered structures is a common phenomenon in our daily life. For many scientific applications, scattering is often treated as a detrimental effect. However, recent development in the field of nanophotonics shows that scattering in disordered nanostructures can enable new functionalities, including the unexpected property of random lasing. A random laser is different from a traditional laser in that the feedback amplification is not provided by a cavity formed by reflection components, but by disorder-induced scattering. Depending on the nature of disordered nanostructures, which can range from a few nanometers to several hundreds of nanometers in size, disorder-induced scattering can provide intensity feedback or amplitude feedback. Thus random lasers are classified into two categories: incoherent random lasers and coherent lasers. During the past two decades, many disordered nanostructures, including laser dye in colloidal systems, photonic crystals, polymeric matrices, rare earth doped nanopowders, quantum dots, semiconductors, and biological tissues have been proposed and demonstrated to form high-performance random lasers. Excitation mechanisms have included optical and electrical pumping. In the former, besides single photon excitation, multiphoton pumped upconversion random lasing has also been demonstrated. In this review, we describe the physics that explains the optical properties of disordered nanostructures and scattering used to develop the random lasers, particularly discussing the role of modes in random lasers. We then present the current state-of-art of fabrication and processing of various disordered nanostructures for the development of random lasers, including techniques to manipulate characteristics such as tunability and directionality. In this context, random fiber lasers will be discussed, as they play an important role in applications of random lasers. It will also be pointed out that random lasers keep the spatial and the temporal coherence characteristic behavior of conventional lasers, as well as the Poissonian statistics well above the threshold. Recent achievements in upconversion lasing, Raman lasing and SPASER lasing in a random medium will also be covered. Then we discuss the impact of random lasers in cross-disciplinary areas such as astrophysics. A major emphasis of this review is to cover the various applications that have already emerged. The review concludes with the author's views on future perspectives, including some envisioned futuristic applications. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a current-steering approach to implement a fast transient response low-dropout regulator (LDO) based on a current feedback amplifier (CFA) topology. The circuit does not require any internal compensation capacitor, being stable for a wide range of output load currents [0–100mA] and a 1μF output capacitor. The CFA consists of an open-loop voltage follower with output local current–current feedback based on a level-shifted flipped voltage follower (LSFVF) which is instrumental to achieve high regulation and fast transient response. The inverting output buffer stage of the CFA together with current-mirror-based driving of the power pass transistor results in high PSRR. Post-layout simulation results for a 0.35μm CMOS process design reveal that the proposed LDO requires 59μA quiescent current at no-load condition and at full-load condition has a current efficiency of 99.8%. For a 1μF output capacitor, the maximum output voltage variation to a 0–100mA load transient with rise and fall times of 10 and 100ns is only 3mV, and the PSRR is smaller than −56dB over the entire load current range. [Copyright &y& Elsevier]

Abstract: In this study, a novel second order universal filter using current-feedback amplifier, commercially available active component, is presented. The signal-flow graph method is used to synthesize the filter. The proposed filter has three high impedance input and one output, (multiple input single output (MISO) configuration). It can generate all biquadratic filtering functions namely: low-pass (LP), band-pass (BP), high-pass (HP), band-reject (BR) and all-pass (AP) at the output terminal by selecting different input signal combinations. The validity of the proposed circuits is demonstrated by simulations. [Copyright &y& Elsevier]

Abstract: In this paper, some new current feedback operational amplifier (CFOA)-based voltage-controlled oscillators (VCOs) have been introduced. The proposed circuits offer a number of advantageous features over previously known CFOA-based VCOs. The workability of the presented circuits has been demonstrated using AD844 CFOAs and BFW10 FETs. [Copyright &y& Elsevier]

Abstract: A full custom analog CMOS circuit for obtaining a photomultiplier readout with a 16bit resolution over 7V has been developed. It is part of the R&D program for the photomultiplier tube front-end readout of the Pierre Auger Observatory northern site. It performs signal duplication and amplification with three gains: 0.15, 1 and 6. Each amplifier has a resolution of 10bit and can measure signals with durations of several microseconds with a good baseline stability, for an input charge of up to tens of nano-Coulombs. The amplification is performed by current feedback amplifiers with a bandwidth of 60MHz.The input impedance, adapted to the coaxial cables, is stable over the whole working range. A prototype was submitted in April 2004 and successfully tested. The linearity over the working range is less than 1%. It was also successfully tested on the Auger surface detector element installed at Orsay (comprised of a Cherenkov water tank equipped with Photonis XP1805 9” diameter photomultiplier tubes). The resolution over 7V is 16.6bit.This circuit is the first step towards a “system-on-a-chip” (SoC) solution for a photomultplier tube readout equipped with a fast ADC for signal digitization. A setup using a single cable for both the signal and the photomultiplier high voltage power supply was shown to be successful. [Copyright &y& Elsevier]

Abstract: In the ISIS facility at Rutherford Appleton Laboratory (RAL) in the UK, a second target station project is in progress. Four 2nd-harmonic RF cavities were installed in the ISIS synchrotron to increase the trapping efficiency, and to mitigate the space charge detuning, allowing a 50% increase in the accelerated beam intensity. A very low-impedance RF system for the 2nd-harmonic cavity was developed by a collaboration of Argonne National Laboratory (US), KEK (Japan) and RAL. The system consists of a 240kW triode as a final-amplifier with plate-to-grid feedback. The measured output-impedance is less than 30Ω over a frequency range of 2.6–6.2MHz. High-power tests were performed using a swept-frequency at 50Hz repetition rate. The operation was stable, and a 6.2kV peak per gap was obtained. The voltage gain of the final-amplifier is 25–30, which gradually decreases with the frequency. A test with beam is planned at ISIS in the near future. [Copyright &y& Elsevier]

In this paper, we provide a new procedure that allows to design a generic three-stage amplifier from settling-time specifications. The procedure analyze the settling-time of pure two- or three-pole amplifiers (i.e., with no zeros) and extends the results to a generic amplifier that includes one or two zeros even placed in the right-half plane. The validity of the proposed approach is demonstrated through a design example of a three-stage CMOS amplifier suitable for switched-capacitor applications. [ABSTRACT FROM AUTHOR]