Inversion Mode Research Articles

A Self-Powered Rectifier-Less Synchronized Switch Harvesting on Inductor Interface Circuit for Piezoelectric Energy Harvesting

In this article, a rectifier-less synchronized switch harvesting on inductor (ReL-SSHI) interface circuit for piezoelectric energy harvesting is presented. The proposed circuit works in two different modes: at the positive peak of the open-circuit voltage of the piezoelectric transducer (PZT), the switch in series with the load is turned on, and is operated in the series synchronized switch harvesting on inductor mode; at the negative peak of the open-circuit voltage of the PZT, the switch in parallel with the load is turned on, and is operated in voltage synchronous inversion mode. The ReL-SSHI circuit does not need a rectifier bridge so that the power loss of the circuit is reduced, and hence the piezoelectric energy harvesting efficiency of the circuit is improved. Theoretical analysis and simulation verify the effectiveness of the ReL-SSHI circuit.

Low power wide tuning range differential ring VCO designs with I-MOS and A-MOS varactor

This manuscript reports two new designs of dual delay cells based on inversion mode MOS (I-MOS) and accumulation mode MOS (A-MOS) varactor for low power and wide tuning range differential ring voltage controlled oscillator (VCO). The new designs obtained a large tuning range by varying the capacitance of the delay stages. The change in capacitance across I-MOS and A-MOS varactor are obtained by varying the gate control voltage (Vg). The proposed VCO circuits are simulated in 0.18 µm CMOS process with a supply voltage (Vdd) of 1.8 V. The tuning ranges of VCO-I (with I-MOS varactor) and VCO-II (based on A-MOS varactor) vary from 1.697–0.714 GHz (81.54%) and 2.019–0.874 GHz (79.15%), whereas their power consumption vary from 4.347–3.507 mW and 3.713–3.063 mW respectively, by modulation of control voltage (Vc) from 0 V to 1 V. The phase noise of ring VCO-I and VCO-II is −103.1 dBc/Hz and −101.2 dBc/Hz at 1 MHz offset from 1.270 GHz and 1.516 GHz central frequency respectively. The figure of merit (FoM) of the VCO-I and VCO-II is −158.92 dBc/Hz and −159.32 dBc/Hz respectively and acquires an area of 0.381 mm2.

Performance Evaluation of Inversion Mode and Junctionless Dual-Material Double-Surrounding Gate Si Nanotube MOSFET for 5-nm Gate Length

In this work, drain current ID for 5-nm gate length with dual-material (DM) double-surrounding gate (DSG) inversion mode (IM) and junctionless (JL) silicon nanotube (SiNT) MOSFET have been studied and simulation results are reported using Silvaco ATLAS 3D TCAD. For this work, we used the non-equilibrium Green's function (NEGF) approach and self-consistent solution of Poisson's equation with Schrodinger's equation. The conduction band splitting into multiple sub-bands has been considered and there is no doping in channel in case of IM SiNT MOSFET. The effect of DM gate engineering for SiNT channel radius 1.5 nm with 0.8-nm gate oxide (SiO2) thickness on ID has been studied. A comparison of results has been done between IM DM DSG and JL DM DSG CGAA SiNT. In case of JL, doping concentration is optimized for two concerns: (i) to get the same IOn current as IM device and (ii) to get the same threshold voltage VTh as IM. This has resulted in 102 and 103 times smaller IOff in matching IOn and VTh optimized device, respectively, as compared to IM. It is found that DM gate engineering reduces drain-induced barrier lowering (DIBL) for both IM and JL SiNT MOSFET. In this work, JL have much smaller DIBL ~15 mV/V, almost an ideal SS ~60 mV/dec, and higher IOn/IOff ratio ~2.18·108 as compared to available CGAA literature results. Keywords: inversion mode, junctionless, DM DSG, Si nanotube MOSFET, NEGF, ID, SS, DIBL.

Dual Active Compensation for Voltage Source Rectifiers Under Very Weak Grid Conditions

DC subgrids consisting of modern active loads (ALs) and local dc distributed generation (DG) units are normally interfaced with the main ac grid by utilizing bidirectional voltage source converters (VSCs). Under the very weak grid (VWG) conditions, the integration of voltage-oriented controlled (VOC) VSCs in the inversion mode becomes very challenging and therefore undamped oscillations in the power and angle responses are yielded. Most of the existing works address this issue for VSCs in the inversion mode of operation. However, integration of VSCs in the rectification mode with the consideration of the outer loop controllers into the VWGs has not been reported. To fill up this gap, a state-space model of the bidirectional VSC-to-weak grid (VSC-WG) system is developed in this work with an emphasis on the rectification mode of operation. A modal-sensitivity analysis is then utilized to evaluate small-signal stability of the system, identify the dominant modes, and investigate the system states that have a major influence on these modes. The results reveal two pairs of unstable complex modes that are correlated with the dynamic interaction between the VOC-based VSCs and the VWG impedance. It is also shown that the stability margin of VSCs in the rectification mode is less than that of the inversion mode under the same VWG conditions. To enhance the integration of the VSCs in the rectification mode, a dual-active compensation (DAC) scheme is proposed to mitigate the instabilities under VWG conditions. Several time-domain simulation results are presented to verify the validity of the small-signal model and demonstrate the effectiveness of the DAC scheme under the VWG conditions. Finally, hardware-in-the-loop (HIL) real-time experimental results are presented to validate the simulation results.

Context-Adaptive Inverse Quantization for Inter-Frame Coding

In the hybrid video coding framework, quantization is the key technique to achieve lossy compression. The information loss caused by the quantization may be reduced to improve compression efficiency, by using either encoder-side rate-distortion optimized quantization or decoder-side filtering. Nonetheless, the existing studies did not extensively use the already encoded information, i.e., context, to reduce the quantization loss. We address this issue and propose a context-adaptive inverse quantization method, namely, CAIQ. Specifically, for inter-frame coding, we analyze the correlation between the prediction signal (generated by motion compensated prediction) and the residual signal, as well as the correlation within the residual signal itself. We then present linear as well as nonlinear yet lightweight models to exploit the observed correlations in the frequency domain. Our models provide an optional inverse quantization mode by referring to the prediction signal, which is available at the decoder side. Next, block-level mode selection regarding the CAIQ method is used at the encoder side. We integrate the proposed CAIQ method into the reference software of Versatile Video Coding. We perform an extensive study of the models and analyze their resulting compression efficiency gain and encoding/decoding complexity. Experimental results show that our CAIQ method improves compression performance especially for high-resolution videos and at high bit rates.

HBC-Based 3Ø System for Wide Range of Power Conversion

The significance of this research work is the hidden bidirectional chopper (HBC) in three-phase systems for the production of a wide range of voltages. Modes of operation in the electrical system ensure productivity and quality, so the proposed system requires four modes of operation. Four modes of approaches are buck rectification, boost inversion, direct rectification, and direct inversion: the first two modes of operation are two-step conversion processes with HBC, where direct inversion and rectification modes exclude HBC for the single-stage operation. HBC is controlled by the standard PI controller to establish output on both sides as a perpetual and three-phase inverter with horizontal switches controlled by the carrier-based pulse width modulation (CBPWM) technique. The system is intended to use quantitative models and initially evaluated on the Simulink platform in MATLAB. Simulation results are validated using a real-time test bench model.

High coupling efficiency, passive alignment setup for visible-range fiber-to-waveguide edge coupling

We present a method to passively edge couple multiple optical fibers with silicon nitride waveguides in the visible wavelengths. We efficiently convert the fiber mode to the waveguide mode using an inverse taper mode size converter and support passive alignment using a U-groove that centers the optical fiber to the inverse taper. In our prototypes, we measure a coupling efficiency of −4.2 dB per facet. To reduce light leakage to the silicon substrate, we use a 6-μm oxide layer, which also eliminates the additional processes of undercutting the silicon substrate underneath the waveguide. Furthermore, the U-groove structure has a polished edge surface for coupling, reducing the steps of edge polishing the die. Fabrication of this visible-range edge coupler is complementary metal–oxide–semiconductor-compatible, making it a highly scalable method for passively packaging multiple visible-range integrated photonics devices.

Analog Operation Temperature Dependence of nMOS Junctionless Transistors Focusing on Harmonic Distortion

This paper performs a comparative study of the analog performance of Junctionless Nanowire Transistors (JNTs) and classical Trigate inversion mode (IM) devices focusing on the harmonic distortion. The study has been carried out in the temperature range of 223 K up to 473 K. The non-linearity or harmonic distortion (HD) has been evaluated in terms of the total and the third order distortions (THD and HD3, respectively) at a fixed input bias and at a targeted output swing. Several parameters important for the HD evaluation have also been observed such as the transconductance to the drain current ratio (gm/IDS), the Early voltage (VEA) and the intrinsic voltage gain (AV). Trigate devices showed maximum AV around room temperature whereas in JNTs the intrinsic voltage gain increases with the temperature. Due to the different AV characteristics, Junctionless transistors present improved HD at higher temperatures whereas inversion mode Trigate devices show better HD properties at room temperature.When both devices are compared, Junctionless transistors present better THD and HD3 with respect to the IM Trigate devices.

Impact of the Series Resistance in the I-V Characteristics of Junctionless Nanowire Transistors and its dependence on the Temperature

The effect of the source/drain parasitic resistance (RS) on the I-V characteristics of Junctionless Nanowire Transistors (JNTs) has been evaluated through experimental and simulated data. The impact of several parameters such as the temperature, the fin width, the total doping concentration, the source/drain length and the source/drain doping concentration on RS has been addressed. The source/drain parasitic resistance presented by JNTs was compared to the one presented by classical inversion mode (IM) triple gate devices, showing opposite behavior with the temperature variation in IM triple transistors and JNTs. In the latter, a reduction on RS is noted with the temperature increase, which is related to the incomplete ionization. This effect inhibits the presence of a Zero Temperature Coefficient (ZTC) operation bias in the Junctionless devices.

Battery voltage equalisation using single‐phase cascaded H‐bridge converters

This research demonstrates modular battery storage systems' voltage balancing using cascaded H-bridge (CHB) converters. The main principle is to maintain AC-side high-quality power absorption or injection, while on the DC-side independent battery units' voltages get balanced. The CHB converter operates in inversion or rectification modes to discharge the storage system to an AC load/grid, or to charge it from an AC source, respectively. To achieve this goal, several challenges as high-differential mode d v / d t , and dealing with semiconductors voltage drop also arise which should get tackled through feasible controller design. Model predictive control (MPC), as a flexible technique capable of multi-parameter controlling, is used to achieve the beforementioned system objectives in a simple, efficient, and scalable manner. The proposed MPC-based algorithm is an AC current controller, which handles DC-side voltage equalisation and introduces adjacent CHB voltage levels to reduce d v / d t and performs switches voltage loss modelling all in a single control block. An additional linear controller based on multi-carrier pulse width modulation is also implemented for comparison with the MPC-based design. Experimental prototyping and simulation results validate the feasibility of this approach.

South African COVID-19 Epidemic Dynamics Are Consistent with Widespread Cross-Immunity

The progression of the Covid-19 pandemic in South Africa, as measured by the number of deaths in excess of the seasonally-expected mortality, is inconsistent with infectivity and fatality rates estimated elsewhere in the world.A compartment model applied in prognostic and inverse mode was used to explore the combinations of key parameters that could account for the outbreak timing and magnitude of Covid-19 mortality in the Western Cape Province in South Africa, where information on reported cases and deaths are most reliable.If it is assumed that the entire population is susceptible, the total number of deaths by October 2020, after six months of propagation, is far lower than expected for fatality and infection rates in the plausible range. The unimodal infection peak, followed by a substantial decline coinciding with the relaxation of non-pharmacological interventions, suggests that herd immunity has been reached, but serological tests for exposure indicate that too few people have been infected for this to be the case. We show that the number of excess deaths, timing of the peak infection and proportion of the population infected can all be explained by assuming 30-40% pre-existing cross-immunity in the population.The dynamics of Covid-19 in South Africa cannot be explained under the assumption of a fully susceptible population. Rather than postulating, against the evidence, that the coronavirus exhibits fundamentally low infectivity or morbidity rates in South Africa, we point out that wide-spread, pre-existing cross-reactive immunity to SARS-CoV-2, could explain the observations. If this is the case, the likelihood of a large second wave is low if those infected do not rapidly lose immunity.Funding Statement: The salaries of Engelbrecht and Scholes are funded by the University of the Witwatersrand. Otherwise, no dedicated source of funding supported this research, and neither author received funding from any source to write the paper.Declaration of Interests: The authors have nothing to disclose.

The effect of magnetic field on efficiency and fouling mechanisms during membrane clarification of pomegranate juice

Microfiltration can be used to clarify Pomegranate juice (PJ); however, it is fouled by charged particles. Magnetic field was coupled with microfiltration to reduce the membrane fouling. Results showed that magnetic field halved the total resistance; since, it increased the permeate flux. The most efficiency of application of the magnetic field in the membrane clarification was achieved at the high intensity of the magnetic field, low level of the feed flow rate and the direction of the magnetic field from the feed to the permeate side. Evaluation of the fouling mechanisms showed that with the increase in the intensity of the magnetic field, at the beginning of the process, the intermediate and standard blockings were dominant mechanisms, but over time, the formation of the cake became more important. Scanning electron microscope (SEM) showed that the layer of the cake deposited on the membrane surface in the absence of the magnetic field, inverse mode with the magnetic field, was very dense. On the other hand, the total monomeric anthocyanin content and the antioxidant activity of PJ increased; pH and total phenolic components were constant, and the total soluble solid content, the turbidity and the acidity were reduced.

Dual Material Gate Engineering to Reduce DIBL in Cylindrical Gate All Around Si Nanowire MOSFET for 7-nm Gate Length

In this work, drain current ID for 7-nm gate length dual-material (DM) cylindrical gate all around (CGAA) silicon nanowire (SiNW) has been studied and simulation results are reported using Silvaco ATLAS 3D TCAD. In this device, we consider the non-equilibrium Green’s function (NEGF) approach and self-consistent solution of Schrodinger's equation with Poisson’s equation. The splitting of conduction in multiple sub-bands has been considered and there is no doping in the channel region. The effect of DM gate engineering (variation of screen gate and control gate length having different work function) for SiNW channel with 2-nm radius and gate oxide (SiO2) thickness of 0.8 nm on ID have been studied. It was found that DM gate engineering reduces drain-induced barrier lowering (DIBL) but it also slightly increases sub-threshold slope (SS). This work has obtained small DIBL (~54 mV/V), small SS (~68 mV/dec), and higher IOn/IOff (~4 × 108) ratio as compared to literature concerning the inversion mode devices. The smallest DIBL is obtained when control gate length is the highest, and vice versa. With increase in control gate length, there is also increase in both IOn and IOff but IOn/IOff ratio decreases.

Inverse Pneumatic Artificial Muscles for Application in Low-Cost Ventilators.

The procurement and maintenance cost of high‐end ventilators preclude their stockpiles sufficient for the mass emergency situations. Therefore, there is a significant demand for mechanical ventilators in such situations. Herein, a low‐cost, portable, yet high‐performance design for a volume‐controlled mechanical ventilator is proposed. Pneumatic artificial muscles, such as air cylinders, are used in the inverse mode of operation to achieve mechanical ventilation. With the current design, the two fundamental modes of operation (controlled mode and assisted mode) are demonstrated. Unlike most intensive care unit ventilators, the proposed device does not need a high‐pressure air pipeline to operate. The device is capable of mechanical ventilation for respiration rate ranging from 10 to 30 b min−1 with a tidal volume (VT) range of 150–1000 mL and the I:E ratio of 1:1–1:5. A total cost of less than $400 USD is achieved to make one device. The cost to produce the device in larger volumes can be estimated to be less than $250 USD.

Simulation of the Nanoscale Joint Surrounding Gate SOI MOSFET Characteristics

In order to solve the current problem of increasing the efficiency of modern electronic circuits, the applicability of a nanoscale joint surrounding gate MOSFET with oval work area is discussed. The design and principle of its operation are considered. This concept involves of jointing the working areas of n-channel and p-channel MOSFETs. In fact, the JSMOSFET consists of two "glued" along the halves of MOSFETs: one - nchannel and the other - p-channel, but with one common gate. We analyze the applicability of the design of an oval-shaped protected area. In our case, the contact of two heterogeneously doped regions occurs in the plane passing through the small axis of the oval. The main channels are formed in zones associated with the large axis of the oval. This achieves the main goalincreasing the number of charge carriers. At the same time, the efficiency of short-channel effect suppression is maintained and a high current level of the transistor is provided in the strong inversion mode. By the developed TCAD model of a nanoscale joint surrounding gate MOSFET with an oval work area the electrophysical characteristics of several prototypes with different transverse dimensions were numerically calculated at a supply voltage of 0.5 V. From the simulation results, it follows that all prototypes are low-voltage devices that can function at voltages below 0.5 V in the gigahertz frequency range with a high gain. The proposed devices perform the function of inverting the input signal without distortion. From the comparison of modeling data, the scope scaling capabilities are determined. The obtained results create prerequisites for the development of the proposed transistor architecture, since electronic chips created on their basis will differ in low power supply voltage, high performance, and minimal occupied area, which meets modern requirements for transistors for analog and digital applications.

Design and Fabrication Approaches of 400–600 V 4H-SiC Lateral MOSFETs for Emerging Power ICs Application

This article reports the demonstration and fabrication of 400-600 V, 4H-SiC lateral MOSFETs on 6-in, N+ substrates. The P-top was implanted on an N- drift region to create a single reduced surface field (RESURF) structure to alleviate the electric field on the surface. The different layout methodologies (source-centered and drain-centered) for making lateral MOSFETs are discussed. The process and design split, such as rapid thermal anneal (RTA) temperatures (900 °C and 1000 °C), different channel designs [accumulation-mode (ACCU) and inversion-mode (INV)], and channel lengths were varied and experimentally analyzed to optimize the device performance. It was confirmed that channel components (channel design and channel length) and RTA temperature are the key ingredients to improve the forward characteristic of the lateral MOSFETs. With the gate to drain length (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gd</sub> ) of 5 μm, the breakdown voltage of 600 V was achieved with a voltage supporting capability of 120 V/μm. On the other hand, a lateral MOSFET with L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gd</sub> of 2.5 μm and with a further reduced channel length (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ch</sub> = 0.3 μm), a record specific ON-resistance of 7.7 mΩ-cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and breakdown voltage of 450 V were achieved. Device design, layout, fabrication, and electrical characteristics of the 400-600 V, 4H-SiC lateral MOSFETs are discussed and reported.

The Role of Solubility in Thermal Field-Flow Fractionation: A Revisited Theoretical Approach for Tuning the Separation of Chain Walking Polymerized Polyethylene.

The influence of the polymer solubility on the separation efficiency in thermal field-flow fractionation (ThFFF) was investigated for a polymer model system of differently branched chain walking polyethylenes in five different solvents, which were selected depending on their physical parameters. The understanding of polymer thermal diffusion has been elucidated using a revisited approach based on the latest thermal diffusion prediction model by Mes, Kok, and Tijssen combined with the Hansen solubility theory. Thereby, a significant improvement in the precision of the thermal diffusion prediction and the separation efficiency has been achieved by implementation of the temperature dependency on Hansen solubility parameters. In addition, we demonstrate a method for validation of the segmental size of polymer chains with varying topology by using the revisited thermal diffusion prediction approach in inverse mode and experimental thermal diffusion data.

Crossing the Nernst Limit (59 mV/pH) of Sensitivity Through Tunneling Transistor-Based Biosensor

In this work, an underlap structure of tunneling field-effect transistor (TFET) containing electrolyte/watery solution is examined to enhance the Nernst limit (59 mV/pH) of sensitivity. After incorporating the electrolyte medium in TFET, effect of pH variation on device characteristics such as drain current vs front gate voltage, voltage sensitivity, and current sensitivity are investigated. The interface charge density at the oxide-silicon interface of TFET is obtained as a function of electrolyte pH from physics-based modelling. Voltage sensitivity value ~180 mV/pH that is greater than three times of Nernst limit of 59 mV/pH and current sensitivity value that is more than one decade per pH are observed for TFET based sensor. In order to validate the results, models used in TFET are well-calibrated with experimental data and the result of TFET are compared with inversion mode (IM) device. Results show that TFET gives superior performance than IM device; hence an underlap TFET can be a promising alternative for the next generation biosensor.

Investigation of f T-Doubler Technique to Improve RF Performance of Inverse-Mode SiGe HBTs

This letter presents the application of the f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> -doubler technique, for the first time, to improve the unitygain frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ) of inverse-mode (TM) silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs). An f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> -doubler structure, which used three identical SiGe HBTs with the same emitter area of 0.07 (width) × 0.9 (length) μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , is implemented in a commercial 0.13-μm SiGe-BiCMOS technology platform. A peak f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> of 77 GHz is extrapolated for the TM f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> doubler, whereas a peak f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> of a single TM SiGe HBT is found to be 53 GHz, exhibiting an increase of about 46% in f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> from the f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> -doubler technique. The maximum oscillation frequency of the TM f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> doubler using Mason's unilateral gain is about 158 GHz. Tn addition, small-signal model parameters of the TM f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> doubler are presented, which show the TM f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> -doubler structures can be treated as a single transistor element for highfrequency circuit design.

From orexin receptor agonist YNT-185 to novel antagonists with drug-like properties for the treatment of insomnia

YNT-185 is the first known small molecule acting as orexin 2 receptor (OX2R) agonist with implication to narcolepsy treatment, served as a template scaffold in generating a small set of seven compounds with predictive affinity to OX2R. The design of the new small molecules was driven mostly by improving physicochemical properties of the parent drug YNT-185 in parallel with in silico studies, later suggesting their favorable binding modes within the active site of OX2R. We obtained seven new potential OX2R binders that were evaluated in vitro for their CNS availability, cytotoxicity, and behavior pattern on OX2R. Out of them, 15 emerged as the most potent modulator of OX2R, which, contrary to YNT-185, displayed inverse mode of action, i.e. antagonist profile. 15 was also submitted to an in vivo experiment revealing its ability to permeate through BBB into the brain with a short half-life.