Search

This study proposes a current-mode KHN universal filter design that can perform three standard functions simultaneously: low-pass, high-pass, and band-pass. The circuit is built around a multiple-output operation transconductance amplifier (MO-OTA), which allows for electronically adjustable pole frequency and quality factor by modifying input bias currents (IB). The circuit layout is straightforward, with two MO-OTAs and two grounded capacitors, eliminating the need for external resistors and depending entirely on grounded components. Because of its simplicity, the circuit is suited for use in a tiny, efficient design. The proposed circuit's operation was validated using LT-Spice simulations, and the results were in line with theoretical expectations. The circuit used around 298µW of power at ±0.2V power supply voltages. These results demonstrate the circuit's potential for low-power applications, which are crucial in many modern electronic devices. The suggested current-mode KHN universal filter offers a viable option for combining various filter functions in a single circuit with customizable parameters. Its simplicity, efficiency, and performance qualities make it a feasible choice for incorporation into a variety of electronic systems, allowing for more filter design freedom [ABSTRACT FROM AUTHOR]

We adopt the tight-binding model and the mode-matching method to study the electrical modulation of the valley polarization in strained silicene constrictions. The effects of the potential energy, the external electric field, and the strain on the band structures and the transport property are investigated. The conductance shows a clear valley polarization and zero conductance in the absence of the electric field and the strain. It is found that the external electric field can open a clear bandgap and result in an extra zero conductance. However, the strain can not induce a bandgap, which only slightly change the energy band. Correspondingly, the strain has little effect on the system's conductance. The transport behavior of zero conductance is elucidated in terms of band structures of the silicene constriction. Therefore, one can realize an effective modulation of the valley-dependent transport of the silicene constriction by combining the potential energy and the electric field. The electrical modulation of the valley polarization and zero conductance can be exploited for silicene-based valleytronics devices. [ABSTRACT FROM AUTHOR]

A thorough study of the admittance of TiN/Ti/HfO2/W bipolar resistive memories [resistance random access memory (RRAM)] was carried out under different bias conditions and in a wide range of ac signal frequencies. We demonstrate that a continuum of intermediate states can be obtained by applying appropriate dc bias waveforms. Cumulative writing and erasing admittance cycles were performed by applying triangular voltage waveform of increasing amplitude. The influence of the initial conditions on the variation of the real (conductance) and imaginary (susceptance) components of the admittance is described. An accurate control of the memory state is achieved both in terms of the conductance and the susceptance by means of an adequate selection of the voltage values previously applied. A method to obtain three-dimensional voltage-conductance-susceptance state-plots is described in detail. Memory maps of admittance parameters as a function of the programming voltage are made by sensing the memory state at 0 V, without static power consumption. The multilevel nature of RRAM devices and their suitability for neuromorphic computation are demonstrated. [ABSTRACT FROM AUTHOR]

A new technique has been developed to determine the high‐latitude electric potential from observed field‐aligned currents (FACs) and modeled ionospheric conductances. FACs are observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE), while the conductances are modeled by Sami3 is Also a Model of the Ionosphere (SAMI3). This is a development of the Magnetosphere‐Ionosphere Coupling approach first demonstrated by Merkin and Lyon (2010), https://doi.org/10.1029/2010ja015461. An advantage of using SAMI3 is that the model can be used to predict total electron content (TEC), based on the AMPERE‐derived potential solutions. 23 May 2014 is chosen as a case study to assess the new technique for a moderately disturbed case (min Dst: −36 nT, max AE: 909 nT) with good GPS data coverage. The new AMPERE/SAMI3 solutions are compared against independent GPS‐based TEC observations from the Multi‐Instrument Data Analysis Software (MIDAS) by Mitchell and Spencer (2003), and against Defense Meteorological Satellite Program (DMSP) ion drift data. The comparison shows excellent agreement between the location of the tongue of ionization in the MIDAS GPS data and the AMPERE/SAMI3 potential pattern, and good overall agreement with DMSP drifts. SAMI3 predictions of high‐latitude TEC are much improved when using the AMPERE‐derived potential as compared to Weimer's (2005), https://doi.org/10.1029/2005ja011270 model. The two potential models have substantial differences, with Weimer producing an average 77 kV cross‐cap potential versus 60 kV for the AMPERE‐derived potential. The results indicate that the 66‐satellite Iridium constellation provides sufficient resolution of FACs to estimate large‐scale ionospheric convection as it impacts TEC. Plain Language Summary: Plasma in the ionosphere convects across high latitudes in response to electric fields generated by solar wind driving of Earth's magnetosphere. Magnetic data from the 66‐satellite Iridium satellite constellation is routinely analyzed to measure the electric currents flowing between the ionosphere and magnetosphere. In this paper, we combined these observed field‐aligned currents with a model of the ionospheric conductance to estimate the corresponding electric field in the ionosphere. We used these electric field estimates to specify the plasma convection in a first‐principles ionosphere model, and compared the results against independent data in a moderately disturbed period. The results of our case study indicate that the technique works well, although plasma convection is not the only factor that causes uncertainty into predictions of the high‐latitude ionosphere. The data used here can be made available in near‐real‐time, so it is possible that our technique could be adopted for operational space weather prediction. Key Points: Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) field‐aligned currents have been combined with the Sami3 is Also a Model of the Ionosphere (SAMI3) model to estimate the high‐latitude potentialIndependent validation of the new technique using satellite drifts and ground‐based total electron content indicates good agreement overallThe SAMI3 model performs better in this case when using AMPERE‐derived potentials than when using the empirical Weimer potential [ABSTRACT FROM AUTHOR]

The down-scaling of nanocrystal Si (nc-Si) floating gate memory must overcome the challenge of leakage current induced by the conventional ultra-thin tunnel layer. We demonstrate that an improved memory performance based on the Al/SiNx/nc-Si/Al2O3/Si structure can be achieved by adopting the Al2O3 tunnel layer fabricated by plasma-enhanced atomic layer deposition. A larger memory window of 7.9V and better retention characteristics of 4.7V after 105 s can be obtained compared with the devices containing a conventional SiO2 tunnel layer of equivalent thickness. The capacitance-voltage characteristic reveals that the Al2O3 tunnel layer has a smaller electron barrier height, which ensures that more electrons are injected into the nc-Si dots through the Al2O3/Si interface. The analysis of the conductance-voltage and high-resolution cross-section transmission microscopy reveals that the smaller nc-Si dots dominate in the charge injection in the nc-Si floating gate MOS device with an Al2O3 tunnel layer. With an increase of the nc-Si size, both nc-Si and the interface contribute to the charge storage capacity and retention. The introduction of the Al2O3 tunnel layer in nc-Si floating gate memory provides a method to achieve an improved performance of nc-Si floating gate memory. [ABSTRACT FROM AUTHOR]

The safe and reliable operation of a modern power system imposes the need to describe and estimate the system stability through impedance‐admittance measurement and identification. The integration and operation of medium voltage equipment in existing infrastructure requires impedance‐admittance measurement devices which are currently few in number and often limited in output voltage level and output bandwidth. The four‐quadrant Cascaded H‐Bridge (CHB) topology, featuring a three‐phase Active Front‐End (AFE) and a single‐phase H‐Bridge inverter presents itself as a potential solution to this problem. To support the development of the CHB topology the AFE hardware and control platforms require implementation and testing. The testing aspect of the process additionally includes the measurement of terminal characteristics such as the input admittance and the output impedance. The complexity of the CHB converter and its increased number of power electronics building blocks requires the use of industrial control platforms. This work defines the hardware implementation and control principle of the three‐phase AFE of a CHB converter as well as the system for measuring its terminal characteristics. The results obtained show that the proposed system can be successfully used to measure the input admittance and output impedance of the AFE upon which the development of the CHB is based. [ABSTRACT FROM AUTHOR]

Admittance-voltage profiling of AlxGa1-xN/GaN heterostructures was used to determine the frequency dependent capacitance and conductance of FET devices in the frequency range from 50 Hz to 1MHz. The nominally undoped low pressure metal-organic vapor-phase epitaxy structures were grown with an Al-content of 30%. An additional 1 nm thick AlN interlayer was placed in one structure before the Al0.3Ga0.7N layer growth. For frequencies below 108 Hz it is convenient to use equivalent circuits to represent electric or dielectric properties of a material, a method widely used, for example, in impedance spectroscopy. We want to emphasize the relation between frequency dependent admittance-voltage profiling and the corresponding equivalent circuits to the complex dielectric function. Debye and Drude models are used for the description of the frequency dependent admittance profiles in a range of depletion onset of the two-dimensional electron gas. Capacitance- and conductance-frequency profiles are fitted in the entire measured range by combining both models. Based on our results, we see contributions to the two-dimensional electron gas for our samples from surface states (80%) as well as from background doping in the Al0.3Ga0.7N barriers (20%). The specific resistance of the layers below the gate is above 105 Ω cm for both samples and increases with increasing negative bias, i.e., the layers below the gate are essentially depleted. We propose that the resistance due to free charge carriers, determined by the Drude model, is located between gate and drain and, because of the AlN interlayer, the resistance is lowered by a factor of about 30 if compared to the sample without an AlN layer. [ABSTRACT FROM AUTHOR]

A linear response method for computing the voltage drop in the high conductance regime is presented. It is applied to the study of both coherent and incoherent transport in model 1D, 2D, and 3D materials, within the non-equilibrium Green's function formalism. The method is shown to accurately reproduce self-consistent voltage drop results computed from first-principles, including the transition from low dimensional screening oscillations to higher dimensional near classical screening. Overall, the method provides an additional analysis technique in the 'quantum transport toolbox' that is complementary to self-consistent methods (in the high conductance regime). [ABSTRACT FROM AUTHOR]

This paper deals with the DC and Radio Frequency (RF) characteristics of InAlAs/InGaAs-based dual-gate high-electron-mobility transistor (DG-HEMT) for a 50 nm gate length. In single-gate HEMT (SG-HEMT), the gate length having less than 100 nm shows poor transconductance (gm) which reduces the voltage gain (Av) and maximum oscillation frequency (fmax). To overcome this problem, a dual-gate structure is designed keeping the device dimensions unchanged and a numerical model is developed to study the effect of the dual gate. A comparative study of SG-HEMT and DG-HEMT is presented. For a DG-HEMT, a maximum drain current (Ids) of 310 mA/mm at Vds = 0.1 V, a peak transconductance (gm_max) of 2294 mS/mm, a cut-off frequency (fT) of 100 GHz and a maximum oscillation frequency (fmax) of 270 GHz have been achieved. For reduced gate length, the DG-HEMT performs better due to the presence of dual gate and double heterojunction. [ABSTRACT FROM AUTHOR]

Single-electron tunneling transistors (SETs) and boxes (SEBs) belong to the family of charge-sensitive electronic devices based on the phenomenon of Coulomb blockade. An SEB is a two-terminal device composed of "leaky," C j , and "non-leaky," C g , nanoscaled capacitors in series. At low temperatures, the charge at the common node is quantized and can only be changed near energy-population degeneracy points, resulting in periodic oscillations of the SEB admittance as a function of voltage applied to C g . In comparison to the SETs, SEBs have higher operating temperature, are electrostatic discharge tolerant, and have a much smaller footprint. To monitor the SEB admittance, Radio Frequency reflectometry can be used. To improve the signal-to-noise ratio, limited by the small change in admittance in an SEB, multiple devices sharing the same source and gate electrodes are connected in parallel to form arrays of SEBs. Due to unavoidable random offset charges, the signal boost for an array of N SEBs is expected to be ∼ N. We experimentally demonstrate that by carefully choosing the operating point, the response to the voltage on the sensing gate can be enhanced, for small arrays scales, by a factor approaching N and, thus, provides a method by which these devices can be used in practical sensing applications, such as a scanning probe. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper analyzes the delayed voltage recovery phenomenon by simplifying the western electricity coordinating council composite load model using the load admittance and the thermal relay dynamics. From this analysis, a closed form expression approximating the recovery time is derived and the key load parameters impacting the behavior of voltage recovery are identified. A monitoring scheme based on the measured load admittance is then proposed to detect the onset of stalling, even in the presence of voltage oscillations, and estimate the duration of the delayed voltage recovery. A mitigation scheme utilizing smart thermostats and offline learning is also derived to ensure that the voltage recovers to the pre-contingency voltage within a specified time. Both the monitoring and mitigation schemes only need local measurements at a substation making them promising for online applications. Results for the monitoring and mitigation schemes are described in detail for the IEEE 162 bus system validating the various assumptions used for the analysis and establishing the connection between the delayed voltage recovery phenomenon and load admittance. [ABSTRACT FROM AUTHOR]

The voltage dependent surface states/traps (Nss) and their relaxation time (τ) of the Al/CdZnO/p- Si (MIS) structure were investigated with admittance method using C-V-f and G/ω-V-f measurements in the frequency range of 5 kHz-1 MHz. Both the values of C and G/ω were found as strong function of voltage and frequency and they increase with decreasing frequency almost for each voltage. The obtained higher values of C and G at the low frequencies are due to the presence of Nss located between CdZnO/p-Si interfaces. At low frequencies, the relaxation time of the charges at the traps is larger than the period (τ≥T) of the applied ac signal, so they can contribute to the measured C and G/ω values. In addition, the presence of Nss causes a peak at the extracted parallel conductance (Gp/ω) versus Lnf curves of the structure. Thus, both the values of Nss and τ were calculated from the peak value and its position, respectively. The values of Nss and τ ranged from 1.65x1013 eV-1 cm-2, 31.4 µs at 1.7 V and 1.39x1013 eV-1 cm-2, 9.18 µs at 3 V, respectively. These values are very suitable for these structures at room temperature. [ABSTRACT FROM AUTHOR]

Action potential generation in neurons depends on a membrane potential threshold and therefore on how subthreshold inputs influence this voltage. In oscillatory networks, for example, many neuron types have been shown to produce membrane potential ( V m ) resonance: a maximum subthreshold response to oscillatory inputs at a nonzero frequency. Resonance is usually measured by recording V m in response to a sinusoidal current ( I app ), applied at different frequencies (f), an experimental setting known as current clamp (I-clamp). Several recent studies, however, use the voltage clamp (V-clamp) method to control V m with a sinusoidal input at different frequencies [ V app (f) ] and measure the total membrane current ( I m ). The two methods obey systems of differential equations of different dimensionality, and while I-clamp provides a measure of electrical impedance [ Z (f) = V m (f) / I app (f) ], V-clamp measures admittance [ Y (f) = I m (f) / V app (f) ]. We analyze the relationship between these two measurement techniques. We show that, despite different dimensionality, in linear systems the two measures are equivalent: Z = Y - 1 . However, nonlinear model neurons produce different values for Z and Y - 1 . In particular, nonlinearities in the voltage equation produce a much larger difference between these two quantities than those in equations of recovery variables that describe activation and inactivation kinetics. Neurons are inherently nonlinear, and notably, with ionic currents that amplify resonance, the voltage clamp technique severely underestimates the current clamp response. We demonstrate this difference experimentally using the PD neurons in the crab stomatogastric ganglion. These findings are instructive for researchers who explore cellular mechanisms of neuronal oscillations. [ABSTRACT FROM AUTHOR]

We investigate the evolution of the electronic transport in disordered NbTiN films at the insulating side of the superconductor-insulator transition as function of the effective system size along the current direction. We demonstrate that both, the threshold voltage characterizing low-temperature superinsulating phase, and the Berezinskii-Kosterlitz-Thouless criticality of the conductance above the superinsulator critical temperature, vanish upon increasing disorder taking the system far from the disorder-driven superconductor-insulator transition. We find that decrease in the system's effective size suppresses its insulating and superinsulating properties and that threshold voltage drops linearly with the diminishing system size. We demonstrate that this linear dependence can be used for experimental measurement of the linear tension of the electric string binding Cooper pairs and anti-Cooper pairs in a superinsulator. [ABSTRACT FROM AUTHOR]

In this paper, a new synchronous machine model is developed for electromagnetic transients program type simulations. The stator circuit is expressed in the abc phase domain. The machine model is represented as a Norton equivalent with a current source in parallel with a constant Norton admittance. The machine equations are reformulated so that the computational effort required for the modeling of the machine is reduced. Test studies demonstrate the accuracy of the proposed synchronous machine model and show that the proposed model is computationally more efficient than the existing constant conductance phase domain model and voltage-behind-reactance model. [ABSTRACT FROM AUTHOR]

In this paper, we formulate and solve the ac optimal power flow (AC-OPF) as an equivalent circuit problem in terms of current, voltage, and admittance state variables. The generator models are represented using conductance and susceptance state variables, and the operational and network constraints are translated to corresponding current/voltage constraints without loss of accuracy or generality. To understand the physics behind the optimality conditions of the optimization problem, we extend the linear adjoint circuit theory to translate them to equivalent circuit domain. It is shown that the operating point that defines the equivalent circuit solution precisely represents an AC-OPF solution. We then further exploit the equivalent circuit representation to use power flow simulation techniques to robustly solve the optimization problem. The efficiency of our approach is demonstrated for several AC-OPF benchmark test cases (up to 70 k buses) under nominal and congested operating conditions, and the runtime and scalability properties are presented. [ABSTRACT FROM AUTHOR]

It is well known that a single (constant power) load infinite-bus system reaches a static voltage stability limit point, or equivalently, a singularity point of the power flow Jacobian, at the unity line-load admittance ratio, i.e., the equivalent admittance of the load has the same modulus as the transmission line admittance. In this paper, we rigorously extend this result to generic distribution systems with distributed generators (DGs). We introduce a new concept called the network-load admittance ratio that is in terms of the parameters of power network, loads, and DGs. This concept is a generalization of the line-load admittance ratio that characterizes the loading status of a distribution system with the effects of DGs included. We prove that the power flow Jacobian is singular if and only if the network-load admittance ratio is unity, which provides new insights into the mechanism of voltage stability. In addition, we establish a new voltage stability index by using the network-load admittance ratio. Numerical simulations on several IEEE test systems show that the index has good linearity with load increase and estimates voltage stability margin with high precision. The index also reflects the impact of DG penetration level and control mode on voltage stability. The obtained results can be extended to ZIP load models, unbalanced three-phase networks, and mesh networks with slight modifications. [ABSTRACT FROM AUTHOR]

In this letter, we investigated negative capacitance (NC) effect in nanocomposite based quantum dot sensitized solar cells. TiO 2 and graphene-TiO 2 nanocomposite photoanode based on quantum dot sensitized solar cells (QDSSCs) were fabricated and the capacitance-voltage (C–V), capacitance-frequency (C-f) and conductance-voltage (G/ω-V) characteristics were studied by attention the series resistance (R s) effect. Admittance spectroscopy of QDSSCs were measured in a variable voltage and frequency ranges of (−2 V) - (+2 V) and 10 kHz-10 MHz, respectively. Capacitance values are exhibited a behavior transition from the positive to negative value after 50 kHz. As the capacitance values decreases, conductance increases in the NC region. Negative capacitance effect of meaning that QDSSC indicates an inductive behavior. Inductive behavior, which means that electrons injects from fluorine-doped tin oxide (FTO) conductive glass electrode to photoanode (graphene-TiO 2). Also, NC phenomenon has not form significant effect on R s. [ABSTRACT FROM AUTHOR]

Continuous models are developed that go beyond the gradual channel approximation and extend MOSFET ${I}$ – ${V}$ characteristics into the velocity saturation region with finite output conductance. Both the ${n} = {1}$ and ${n} = {2}$ models have been employed. It is shown that the standard relation of channel length modulation for constant mobility must be modified for velocity saturation because the drain current is not simply inversely proportional to the channel length. Regional approximations are applied to derive the explicit expressions for the output conductance in the velocity saturation region in terms of basic device parameters. [ABSTRACT FROM AUTHOR]

Hydrogenated diamond MOSFETs with self-oxidized alumina as a gate dielectric are fabricated. The diamond MOSFETs show a high maximum drain current density of 466 mA/mm at VGS = −6 V, a transconductance of 58 mS/mm, and an off-state breakdown voltage of −53 V. The maximum output power density reaches 745 mW/mm at 2 GHz continuous wave, which is the highest reported value for diamond transistors measured at 2 GHz. The output power value measured is lower than that estimated. Pulse I-V analysis shows that the main factor that affects the output power of the diamond MOSFETs is the traps in the channel. [ABSTRACT FROM AUTHOR]

In this paper, a multiple-input single-output (MISO) voltage-mode bi-quad active filter using voltage differencing voltage transconductance amplifier (VDVTA) is designed and analysed. The filter can realize several functions such as low-pass (LP), high-pass (HP), band-pass (BP), band-reject (BR) and all-pass (AP). The proposed configuration employs three input voltages and generates a single output voltage. The filter characteristics, i.e., pole frequency (ωp) and quality factor (Q) are electronically tunable through the bias current of the VDVTA. The filter performance is analysed through sensitivity analysis in presence of parasitics as well as process, voltage and temperature fluctuations. The proposed design is implemented in a 45-nm CMOS technology and simulated using Virtuoso Analog Design Environment of Cadence. [ABSTRACT FROM AUTHOR]

An ultra-low-power process-insensitive two-stage OTA working in weak inversion region with enhanced transconductance and DC gain is presented in this paper. The proposed two-stage OTA is based on a bulk-driven input stage with rail-to-rail input voltage range, in which the bulk transconductance is enhanced by means of a partial positive-feedback loop. At the same time, a pseudo-cascode frequency compensation technique is applied in this design to improve the phase margin and accordingly, robust the stability of the proposed OTA. In addition, the proposed composite-transistor structure is used to improve output impedance of the two-stage OTA in weak inversion region. As a result, the improvement of DC gain and gain-bandwidth is obtained. Transistor-level simulations and results in UMC 0.18 μm CMOS process confirm the theoretical results. Simulated from a 0.5 V supply voltage, the proposed two-stage OTA achieves a 111.5 dB DC gain, a gain-bandwidth product of 9.5 kHz and a phase-margin of 66∘ while driving a 15 pF load. [ABSTRACT FROM AUTHOR]

Highlights • A current sensorless maximum power point tracking (MPPT) algorithm is proposed. • Drift-free technique is achieved and high tracking efficiency is realized. • A mathematical expression is obtained for the drift-free criterion. • Threshold is determined by the Lambert W function under the EN50530 standard. • The proposed algorithm was experimentally evaluated under different scenarios. Abstract High system cost and reduced output power due to the changing weather conditions such as the irradiance or temperature are two major concerns for a practical photovoltaic (PV) system design. This paper presents a current sensorless (CS) maximum power point tracking (MPPT) algorithm that uses only one single-input-voltage sensor (SIVS) and totally eliminates the expensive current sensors, which can significantly reduce the system cost and retain the advantages of the widely used MPPT algorithms such as incremental conductance (INC). To further eliminate the drift effect, which is a severe phenomenon due to the incorrect decision in duty cycle for fast irradiation change, drift-free technique is adopted in the presented algorithm by incorporating the information of change in duty cycle (Δ D) and change in input voltage (Δ V). A mathematical expression is given to define the drift-free criterion and the threshold is determined by the Lambert W function with respect to the dynamic EN50530 test standard. Experimental results under different scenarios are presented to validate the advantages of the presented method in terms of the tracking efficiency and drift-free characteristic. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the conduction mechanisms in MOS structures are investigated using Normalized Differential Conductance (NDC). It is shown that NDC can be applied successfully for the determination of conduction mechanism parameters in MOS devices. The method allows the separation of various components of conduction current and determines the permissible voltage ranges for the determination of the conduction mechanism parameters through the device. The procedure is illustrated by applying it to simulated and experimental current-voltage (I-V) characteristics. The limitations of such parameters extraction are also investigated. A qualitative favorable comparison between experimental data and simulated results is also obtained. [ABSTRACT FROM AUTHOR]

In this article, we have demonstrated junctionless operation in ringFET structure on <100> silicon bulk substrate using threedimensional numerical simulations, for channel lengths below 100 nm. On current, OFF/leakage current, ON to OFF current ratio, transconductance, threshold voltage, subthreshold slope, output resistance and unity gain frequency of the device are extracted. Channel length, drain radius, epi-layer thickness and epi-layer doping of the device are varied to investigate their impact on the device performance, using the above performance metrics. A brief comparison with the junction-based ringFET device is also provided. [ABSTRACT FROM AUTHOR]

Abstract: The work realizes the sinusoidal quadrature oscillator and biquadratic filter with the same configuration using merely two voltage differencing transconductance amplifiers (VDTAs) as active devices and one grounded resistor and two grounded capacitor as passive elements. Performing the quadrature oscillator, the realized circuit is capable of producing two quadrature voltage outputs with almost equal amplitudes, and an independent electronic control of oscillation condition and oscillation frequency. Operating in voltage-mode biquadratic filter, the circuit can simultaneously generate the bandpass and lowpass filtering functions without any matching constraints. The natural angular frequency and the quality factor of the filter are independently and electronically adjustable. The effects of the VDTA non-idealities are also investigated in detail. Simulation results with TSMC 0.25 μm CMOS technology validate both working functions of the proposed circuit. [ABSTRACT FROM AUTHOR]

Gap junction (GJ) channels are oligomers of connexins forming channels linking neighboring cells. GJs formed by different connexins show distinct unitary channel conductance (γj), transjunctional voltage-dependent gating (Vj-gating) properties, and modulation by intracellular magnesium ([Mg2+]i). The underlying molecular determinants are not fully clear. Previous experimental evidence indicates that residues in the amino terminal (NT) and initial segment of the first extracellular (E1) domain influence the γj, Vj-gating, and/or [Mg2+]i modulation in several GJs. Increasing negatively charged residues in Cx50 (connexin50) E1 (G46D or G46E) increased γj, while increasing positively charged residue (G46K) reduced the γj. Sequence alignment of Cx50 and Cx37 in the NT and E1 domains revealed that in Cx50 G8 and V53, positions are negatively charged residues in Cx37 (E8 and E53, respectively). To evaluate these residues together, we generated a triple variant in Cx50, G8E, G46E, and V53E simultaneously to study its γj, Vj-gating properties, and modulation by [Mg2+]i. Our data indicate that the triple variant and individual variants G8E, G46E, and V53E significantly increased Cx50 GJ γj without a significant change in the Vj gating. In addition, elevated [Mg2+]i reduced γj in Cx50 and all the variant GJs. These results and our homology structural models suggest that these NT/E1 residues are likely to be pore-lining and the variants increased the negative electrostatic potentials along the GJ pore to facilitate the γj of this cation-preferring GJ channel. Our results indicate that electrostatic properties of the Cx50 GJ pore are important for the γj and the [Mg2+]i modulation. [ABSTRACT FROM AUTHOR]

Abstract In this paper a new active resistor is proposed which is suitable for tunable linear voltage to current converters. The proposed resistor is composed of the main and auxiliary triode-mode transistors in which the resistance of auxiliary transistor adds to that of main transistor at a specific tune voltage. By this way the triode operation of both transistors is ensured throughout the tuning range. The proposed resistor is used in a tunable linear transconductor. The proposed transconductor which is implemented in 0.13 μm CMOS technology works with 1.2 V supply voltage and its power consumption changes between 682 and 980 μW. Simulation results show 20 dB improvement in THD of transconductor thanks to using proposed resistor rather than conventional one for input voltage amplitude of 1Vpp at 1 MHz. The transconductance can be tuned from 68 to 177.4 μA/V and the THD remains less than −55 dB for input voltage amplitudes up to 1.2Vpp and for the entire tuning range. [ABSTRACT FROM AUTHOR]

The aim of this paper is to apply Thevenin’s theorem to mutually coupled elements. Mutual coupling between elements exist due to proximity of elements in electric circuits. The determination of the current in a new added element to an existing circuit is usually done through Thevenin’s theorem when the new element is not mutually coupled with any other element in the circuit. However, when the element is mutually coupled with other elements in the circuit, then application of Thevenin’s theorem is not straightforward. Thevenin’s voltages and impedances have to be modified to include the effect of mutual coupling between the new element and the existing elements of the circuit. A systematic approach to modify Thevenin’s voltages and impedances is presented in this paper. Two examples are presented to demonstrate the procedure. The first example considers only single coupling while the second considers multiple coupling. In single coupling, the new element is coupled only with a single element of the circuit. In multiple coupling, the element is coupled with several elements of the circuit. [ABSTRACT FROM AUTHOR]

To provide radiation hard device is very critical and when a new technology come into existence it becomes more challenging. In this research paper we have explored the radiation response of hafnium dioxide (HfO2)/silicon (Si) structure based metal oxide semiconductor (MOS) capacitor on p-type substrate, subjected to 2.7 MeV proton irradiation at various fluencies (3.6 × 1012 protons/cm2, 7.2 × 1012 protons/cm2, 1.08 × 1013 protons/cm2, 1.8 × 1013 protons/cm2, 2.16 × 1013 protons/cm2 and 3.6 × 1013 protons/cm2). Through electrical characteristics, radiation hardness of atomic layer deposited HfO2 based MOS capacitor has been investigated. To directly measure interface charge and to evaluate its change with the ionizing doses, capacitance-voltage (C-V) and conductance-voltage (G-V) measurements are taken. To provide an evidence for the change in the device parameters pre and post-irradiation curves are plotted to compare the degradation of the device. Shift in C-V and G-V characteristics were observed in irradiated devices that also indicate a change in flat band voltage, midgap voltage and conductance of devices. Generation of new traps after proton irradiation was also confirmed by these measurements. [ABSTRACT FROM AUTHOR]

To provide radiation hard device is very critical and when a new technology come into existence it becomes more challenging. In this research paper we have explored the radiation response of hafnium dioxide (HfO2)/silicon (Si) structure based metal oxide semiconductor (MOS) capacitor on p-type substrate, subjected to 2.7 MeV proton irradiation at various fluencies (3.6 × 1012 protons/cm2, 7.2 × 1012 protons/cm2, 1.08 × 1013 protons/cm2, 1.8 × 1013 protons/cm2, 2.16 × 1013 protons/cm2 and 3.6 × 1013 protons/cm2). Through electrical characteristics, radiation hardness of atomic layer deposited HfO2 based MOS capacitor has been investigated. To directly measure interface charge and to evaluate its change with the ionizing doses, capacitance-voltage (C-V) and conductance-voltage (G-V) measurements are taken. To provide an evidence for the change in the device parameters pre and post-irradiation curves are plotted to compare the degradation of the device. Shift in C-V and G-V characteristics were observed in irradiated devices that also indicate a change in flat band voltage, midgap voltage and conductance of devices. Generation of new traps after proton irradiation was also confirmed by these measurements. [ABSTRACT FROM AUTHOR]

In this work, a new differential topology of Colpitts VCO with an enhanced transconductance is presented. The proposed circuit is consisted of an NMOS and a PMOS differential Colpitts cores configured as complementary, and also an LC resonator. The VCO is designed to oscillate at 5 GHz which consumes 1.11 VA from 1.4 V supply voltage. In addition, a modified version of the proposed VCO is designed for lower power applications. This circuit employs new positive feedbacks to enhance the VCO’s transconductance and reduce the supply voltage. The modified VCO operates with 1.1 V power supply while dissipating 1 mW. To investigate the performance of the proposed circuits, the transconductance of them are theoretically analyzed. Also, two new quadrature VCOs (QVCOs) are presented which are realized by two identical latter proposed Colpitts VCOs. A linear analysis is presented to confirm that the first oscillator can generate outputs with 90° phase differences. The proposed circuits are designed in 0.18-μm RF-CMOS technology. Finally, prototype circuits of the proposed VCOs are fabricated to validate the theoretical results. The measurement results are summarized to demonstrate the main features of the proposed oscillators. [ABSTRACT FROM AUTHOR]

The paper proposes a frequency-domain harmonic model for 12-pulse series-connected thyristor-controlled rectifier under unbalanced supply voltage, considering the firing angle offset and commutation overlap angle caused by unbalanced voltage. The harmonic coupled admittance matrix of 12-pulse rectifier is derived based on positive-sequence and negative-sequence voltages for the frequency-domain harmonic model. The simplified model of 12-pulse rectifier that only considers the primary matrix elements is proposed by comparing the values and distribution of admittance matrix elements under positive-sequence and negative-sequence voltages and analyzing the harmonic production process of the AC current of rectifier. The application condition of different simplified models is investigated by analyzing the calculation errors changing with the firing angle or commutation overlap angle. The accuracy and efficiency of the proposed models is verified by simulation and experimentation. [ABSTRACT FROM AUTHOR]

Abstract A super class AB-AB bulk-driven folded cascode operational transconductance amplifier (OTA) with improved slew rate and unity-gain bandwidth is presented. The proposed bulk-driven amplifier utilizes the adaptively biased circuits, the bulk-driven flipped voltage follower and quasi-floating gate circuit, to implement the class-AB input stage and class-AB output stage respectively, which provides enhanced unity-gain bandwidth and dynamic current boosting. The proposed bulk-driven OTA is simulated on the 0.18 μm SMIC process with 1 V low voltage supply. The simulation results show that the proposed class AB-AB bulk-driven OTA achieves the increased factor of 6.5 and 4.7 in unity-gain bandwidth and slew rate compared with that of conventional class-A counterpart with only 50 % extra power consumption. Highlights • The BFVFs are applied in input stage to achieve class-AB operation, improving GBW. • The QFG technique is utilized in output stage to form the class-AB output stage which enhances the GBW and SR. • The value of FoM in our proposed SBDFC OTA confirms that our proposed bulk-driven OTA has better current efficient. [ABSTRACT FROM AUTHOR]

We use the energy analysis as a perturbative method to study the effect of electron-radial breathing mode (RBM) phonon interaction on the electrical conductance of long metallic zigzag carbon nanotubes (CNTs). The band structure of zigzag CNTs is calculated by exerting zone-folding method on relations derived by using the nearest neighbor approximation of tight-binding expression for the π bands of graphene. The small hollow cylinder model, with two different approximations, is used to obtain the RBM frequency in our calculation. As the result, we have calculated the effects of electron−RBM phonon interaction on the conductance of zigzag CNTs. It has been observed that current is a step−like function of bias voltage due to the absorption or emission by electron injection in the system. Moreover, the dependence of the conductance to the temperature in low bias and high bias voltages has been studied. In this paper, we propose a simple and useful method for phonon spectroscopy. Also, since RBM mode determines the geometry and structure of CNT, this approach can be used for characterization of CNTs. [ABSTRACT FROM AUTHOR]

We investigated an Electrolyte-Gated Organic Field-Effect transistor based on poly(N-alkyldiketopyrrolo-pyrrole dithienylthieno[3,2-b]thiophene) as organic semiconductor whose gate electrode was functionalized by electrografting a functional diazonium salt capable to bind an antibody specific to 2,4-dichlorophenoxyacetic acid (2,4-D), an herbicide well-known to be a soil and water pollutant. Molecular docking computations were performed to design the functional diazonium salt to rationalize the antibody capture on the gate surface. Sensing of 2,4-D was performed through a displacement immunoassay. The limit of detection was estimated at around 2.5 fM. [ABSTRACT FROM AUTHOR]

Abstract With scanning tunneling spectroscopy (STS), we have recorded voltage-dependent differential conductance (d I /d V) images of P3HT:PCBM bulk-heterojunctions (BHJs). Since the materials are seen "energetically" in d I /d V images, the imaging process has provided opportunities to view the nano-domains of the components in the BHJ. When the images were recorded at different voltages, energy-levels at the interface region between two hetero-domains could be viewed energetically. As such, the density of states (DOS) spectra of pristine materials provided location of energy levels of the polymer and the fullerene in forming energy diagram with a type-II alignment from the view-point of charge carriers. DOS spectra recorded in the P3HT:PCBM heterojunction in addition yielded energies that deviated from those of the components in the BHJ. These energies along with bias-dependent d I /d V images evidenced that the interface region between P3HT and PCBM domains possessed energy levels intermediate to those of the components. Graphical abstract Image 1 Highlights • Voltage-dependent d I /d V images of P3HT:PCBM bulk-heterojunctions. • The images allowed viewing of polymer and fullerene nano-domains. • Differential conductance images provided energy-mapping of the heterojunction. • The voltage-dependent images allowed viewing of the interface region as well. [ABSTRACT FROM AUTHOR]

Partial Shading plays a vital role in the power generation from PV arrays. It can drastically reduce the power output from PV arrays resulting in multiple maximum peak points in power-voltage characteristics. The power reduction in PV arrays less depends on area of shading but significantly depends on the pattern of shading. In this paper, a static shade dispersion positioning (SDP) technique for modules of PV array to the reduce power loss caused by partial shading has been proposed. The technique aims to reduce the power loss by distributing the effect of partial shading into whole array without changing the electrical configuration of the system. The performance of the proposed technique has been compared with the existing hitherto known conventional topologies i.e. Series-Parallel, Bridge-Linked and Total Cross Tied under various non-uniform and uniform shading conditions. The comparison is done for a 3 × 3 PV array using MATLAB and a prototype field experiment. Also, the proposed SDP technique has been compared with Su Do Ku arrangement and EAR strategy. It is found that the proposed SDP technique excels in performance by maximizing the power generation of PV arrays under various shading conditions and can be easily implemented in field conditions without any complexity. [ABSTRACT FROM AUTHOR]

This paper presents a supper class-AB adaptive biasing bulk-driven amplifier for ultra-low-power applications. In the proposed structure, two bulk-driven flipped voltage follower (FVF) cells are reconfigured as nonlinear tail currents using quasi-floating gate method to enhance transconductance and slew rate. In addition, two idle current controllers are employed as common source amplifiers to provide a supper class-AB structure without increasing total current consumption. The proposed structure is simulated in 0.18-m CMOS technology at 0.5V supply with 35nW power budget. The results show a 57.9dB DC gain, 8.8kHz gain bandwidth and 38.2V/ms slew rate for the proposed amplifier. [ABSTRACT FROM AUTHOR]

Currently, the most widespread alternative fuel systems for combustion engines are low-pressure gas ones. When configuring such types of systems or when attempting to initiate simulation research, the flow characteristics of individual subassemblies, particularly the injectors need to be known. The equipment manufacturers only provide the volumetric flow rate at a given pressure without indicting whether the measurement was carried out under standardized guidelines. Therefore, the author attempted to determine the flow characteristics of low-pressure vapor-phase injectors using the ‘tank’ method following the guidelines of the JIS B 8390 standard. The copyrighted algorithm of throughput identification has been developed based on the flow model using the lumped elements method. Characteristics were determined depending on the injection time and depending on the opening frequency of the injector and linear increments in the investigated ranges were observed. The coefficient of determination adjusted to the degrees of freedom in both cases exceeded 99.9%. Compliance of the measurements using the proposed method with the flow meter measurements was confirmed. The maximum differences sometimes exceeded 5%. The paper presents the variability of the mass flow depending on the injection time and depending on the opening frequency of the injector. This is a basis in the course of modeling of the operation of engines or the assessment of the fuel consumption in simulation models of standardized driving cycles. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a comprehensive approach to frequency compensating multistage amplifiers. Different stage cases have been considered namely, differential voltage and current blocks, and general compensation blocks for both voltage and current states. Then, a matrix description has been proposed to describe the configurations. The approach involved binary matrixes in order to model amplifiers with feedback networks. Evolutionary algorithms were used to find optimum numerical values and simplify symbolic transfer functions. Also a diagram-based design was used to find the appropriate MOSFET DC bias conditions and dimensions. Note that using simplified transfer functions to symbolically locate the poles and zeroes allowed a better circuit design knowledge compared to numerical approaches. To demonstrate the proposed procedure, two circuit were designed in TSMC 0.18 μm CMOS technology and simulated results successfully compared to linear models extracted from the matrix description. According to simulations, the proposed configurations in both voltage and current states show excellence performance versus previous works. Finally, special design cases such as multi-compensation blocks and N-stage approach were discussed. [ABSTRACT FROM AUTHOR]

The stability of a grid-connected system (GCS) has become a critical issue with the increasing utilization of renewable energy sources. Under grid faults, however, a grid-connected inverter cannot work efficiently by using only the traditional droop control. In addition, the unbalance factor of voltage/current at the common coupling point (PCC) may increase significantly. To ensure the stable operation of a GCS under grid faults, the capability to compensate for grid imbalance should be integrated. To solve the aforementioned problem, an improved voltage-type grid-connected control strategy is proposed in this study. A negative sequence conductance compensation loop based on a positive sequence power droop control is added to maintain PCC voltage balance and reduce grid current imbalance, thereby meeting PCC power quality requirements. Moreover, a stable analysis is presented based on the small signal model. Simulation and experimental results verify the aforementioned expectations, and consequently, the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

A double-gate MOSFET model that goes beyond the gradual channel approximation is developed by incorporating the effect of lateral field gradient on carrier density. It is shown that while the oxide field crosses zero at the point of saturation and becomes negative beyond it, the channel is not pinched off of charge carriers. The model generates $\text {I}_{\text {ds}}$ – $\text {V}_{\text {ds}}$ characteristics continuous into the saturation region with the finite output conductance consistent with TCAD. An explicit expression is derived for the output conductance in saturation in terms of basic device parameters. [ABSTRACT FROM AUTHOR]

Electrical characteristics of the Au/Si3N4/4H n-SiC metal-insulator-semiconductor (MIS) diode were investigated under the temperature, T, interval of 160-400 K using current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements. Firstly, the Schottky diode parameters as zero-bias barrier height (ΦB0) and ideality factor (n) were calculated according to the thermionic emission (TE) from forward bias I-V analysis in the whole working T. Experimental results showed that the values of ΦB0 were in increasing behavior with increasing T while n values decreased with inverse proportionality in n versus ΦB0 plot. Therefore, the non-ideal I-V behavior with inhomogeneous barrier height (BH) formation has been discussed under the assumption of Gaussian distribution (GD). From the GD of BHs, the mean BH was found to be about 1.40 eV with 0.1697 standard deviation and the modified Richardson constant A∗ of this diode was obtained as 141.65 A/cm2 K2 in good agreement with the literature (the theoretical value of A∗ is 137.21 A/cm2 K2). The relationship between ΦB0 and n showed an abnormal I-V behavior depending on T, and it was modeled by TE theory with GD of BH due to the effect in inhomogeneous BH at the interface. Secondly, according to Cheung’s model, series resistance, RS values were calculated in the T range of 160-400 K and these values were found to decrease with increasing T. Finally, the density of interface states, Dit was calculated and the T dependence of energy distribution of Dit profiles determined the forward I-V measurements by taking into account the bias dependence of the effective BH, Φe and n. Dit were also calculated according to the Hill-Coleman method from C-V and G/ω-V analysis. Furthermore, the variation of Dit as a function of frequency, f and T were determined. [ABSTRACT FROM AUTHOR]

This paper proposes two techniques for the identification of critical buses in a power system. The technique of Network Structural Theory Participation Factor (NSTPF) depends on the network structural interconnection of buses as captured by the admittance matrix of the system and is formulated based on the fundamental circuit theory law using eigenvalue decomposition method. Another power flow based technique which depends on the system maximum loadability, the system step size among other factors is also proposed. Traditional power flow based techniques are used as benchmarks to determine the significance of the proposed methods. To ensure voltage stability enhancement, STATCOM FACTS device is installed at the selected weak load buses of the practical Nigerian 24 bus and IEEE 30 bus test systems. The results of the simulation obtained show that, the suggested approach of NSTPF is more suitable in the identification of weak buses that are liable to voltage instability in power systems as it requires less computational burden and also saves time compared to techniques based on power flow solutions. [ABSTRACT FROM AUTHOR]

Tens of graphene transistors with nanoperforated channels and different channel lengths were fabricated at the wafer scale. The nanoholes have a central diameter of 20 nm and a period of 100 nm, the lengths of the channel being of 1, 2, 4 or 8 μm. We have found that the mobility in these 2 μm-wide transistors varies from about 10400 cm 2 /Vs for a channel length of 1 μm to about 550 cm 2 /Vs for a channel length of 8 μm. Irrespective of the mobility value, in all transistors the on-off ratio is at least 10 3 at drain and gate voltages less than 2 V. The channel length-dependent mobility and conductance values indicate the onset of strong localization of charge carriers, whereas the high on-off ratio is due to bandgap opening by nanoperforations. [ABSTRACT FROM AUTHOR]

A novel circuit of square/triangular wave generator consists of single multiple output dual-X current conveyor transconductance amplifier (MO-DXCCTA), one grounded resistor and one grounded capacitor is proposed. One square wave in current mode and one triangular wave in voltage mode are simultaneously available from the proposed generator. The proposed circuit is fully electronically controllable facilitating the feature of duty cycle adjustment. The duty cycle is electronically tunable via bias current. Moreover, a wide sweep of oscillation frequency is possible via grounded capacitor with very good linearity. The tuning of oscillation frequency does not affect the amplitudes of output waveforms. Furthermore, the oscillation frequency can also be controlled electronically and independently via bias current for a fixed duty cycle of 50%. A prototype of MO-DXCCTA using commercial ICs (AD844 and LM13700) is used to carry out the experimental results. Measured results show very good variation of frequency (up to 245.5 kHz) against capacitor with nonlinearity less than 2%. [ABSTRACT FROM AUTHOR]

Stability of low voltage regulated cascode (RGC) transimpedance amplifier (TIA) with level shifter path is analyzed and criterions for a well-behaved time response are derived. It is shown that there is a trade-off between the amplifier bandwidth and stability in this topology. Improving bandwidth by increasing transconductance of transistors leads to ringing in the step response of the amplifier and finally its instability. To add a degree of freedom to design of the low-voltage RGC circuit for high-speed optical receivers, a compensation technique is proposed in this paper and employed in a TIA circuit, designed in a 0.18 μm CMOS technology. Post layout simulation results show a gain of 52 dBΩ and bandwidth of 3 GHz in presence of a 2 pF photo-detector (PD) capacitance and with power consumption of 4.3 mW. The results show that the proposed technique enhances bandwidth of the low-voltage RGC circuit by about 40%, while preserving its stability and well-behaved time response. [ABSTRACT FROM AUTHOR]