1. In designing a circuit, the current through each LED must not exceed the absolute maximum rating specified for each LED. In the meanwhile, resistors for protection should be applied, otherwise slight voltage shift will cause big current change, 1. Static electricity or surge voltage damages the LEDs. Damaged LEDs will show some unusual characteristic such as the forward voltage becomes lower, or the LEDs do not light at the low current. even not light.
DOI: 10.4236/ojbiphy.2019.94017 241 Open Journal of Biophysics the sequencing mechanisms of sensors based on ISFETs can actually be used only for detecting nucleic acid using pH sensitivity and amplifying the useful signal in real time. Static, dynamic characteristics and pH sensitivity of bio FET sensors made on nanosize silicon (nanowire, nanoribbon) are detailed study by us in   . In  pH sensitivity of the biochemical sensors was intro- duced as ∆ I ds ∆ pH , where, ∆ I ds and ∆ pH are the elementary changes in
As far as steady state analysis is concerned, both configurations can modeled along similar lines, The SVC structure shown in Fig. 1 is used to derive a SVC model that considers the Thyristor Controlled Reactor (TCR) firing angle as state variable. This is a new and more advanced SVC representation than those currently available. The SVC is treated as a generator behind an inductive reactance when the SVC is operating within the limits. The reactance represents the SVC voltage regulation characteristic. The reason for including the SVC voltagecurrent slope in power flow studies is compelling. The slope can be represented by connecting the SVC models to an auxiliary bus coupled to the high voltage bus by an inductive reactance consisting of the transformer reactance and the SVC slope, in per unit (p.u.) on the SVC base. A simpler representation assumes that the SVC slope, accounting for voltage regulation is zero. This assumption may be acceptable as long as the SVC is operating within the limits, but may lead to gross errors if the SVC is operating close to its reactive limits . The current drawn by the SVC is, I SV C jB SV C .V K
2.1 Leakage current control using transistor stack The leakage current flowing through a stack of series connected transistors reduces when more than one transistor of the stack is turned OFF. This effect is known as the ―Stacking Effect‖. When two or more transistors that are switched OFF are stacked on top of each other (refer fig.1.a) then they dissipate less leakage power than a single transistor that is turned OFF(fig.1.b). This is because each transistor in the stack induces a slight reverse bias between the gate and source of the transistor right below it, and this increases the threshold voltage of the bottom transistor making it more resistant to leakage. Therefore in fig. 1(a) transistor T2 leaks less current than transistor T1 and T3 leaks less than T2. Hence the total leakage current through the transistors T, T2 andT3 is decreased as it flows from Vdd to Gnd. So Ileak1 is less than Ileak2. If natural stacking of transistors do not exist in a circuit, then to utilize the stacking effect a single transistor of width W is replaced by two transistors each of width W/2 ————————————————
The PV cell has non–linear current–voltage qualities. The power delivered by an array increases to a point, as the current draw rises. The maximum power point is usually at the knee of the curve. The aim of the MPPT subsystem is to determine just where that point is, and to regulate current accordingly. The factors that make the location and tracking the maximum power point a bit more challenging are temperatures and the partial shading of an array. The rapid changes in irradiance or temperature may introduce multiple local maxima. Some MPPT techniques address the issue of phantom maxima better than others .
The proposed model allows us to reproduce both the transient and frequency IGBT module behaviour. Figure 8 shows the PSpice simulated output voltage and the respective zoom at f=1MHz and Vin=25mVpp, input signal. The collector current and voltage are Ic=100A and Vce=300V, respectively. The simulated waveforms are very similar to those observed in Figure 2. Moreover the proposed model reproduces very accurately the IGBT module high frequency Bode diagram. Figure 9 shows a comparison between experimental (solid line) and simulated (dotted line) frequency behaviour for a supply voltage of 350V and a collector current of 200A. A quite good accuracy can be recognized. Moreover, from the analysis of Figure 9, we can recognize a peak in the frequency response at about (20MHz) that is quite well reproduced also by the proposed model. This peak seems to be of the same nature of the resonant peaks measured on the same modules .
Wide application of power electronic based equipment has resulted in a serious impact on the nature of electric power supply. Smooth uninterrupted sinusoidal voltage at desired magnitude and frequency should always be provided to the consumers. On the other hand consumers should draw sinusoidal current . Efforts are being made by many researchers for the effective improvement of power quality. UPQC is considered as the most powerful solution to the problems arising due to power quality. It is adequate enough to take care of supply voltage disturbances like voltage sag/swells, voltage flickers, load reactive power as well as voltage and current harmonics. The UPQC can also be named as the universal active power line conditioner, universal power quality conditioning system and also universal active filter. It is a cascade connection of series and shunt active power filter (APF) connected through a common DC link capacitor . Poor power quality affects electricity consumers in many ways. The poor power quality may result into loss of production, damage of equipment or appliances, increased power losses, interference with communication lines etc. The decline quality of electric power is mainly because of current and voltage harmonics due to wide range application of static power electronics converters, zero and negative sequence component originated by the use of single phase and unbalanced load, reactive power, voltage sag, voltage swell, flicker, voltage interruption etc. Therefore, it is very crucial to maintain a standard power quality. The series APF is coupled to the supply line through a series transformer. The series APF prevents the source side voltage disturbances from entering into the load side to make the load voltage at desired magnitude and frequency . Whereas the shunt APF connected in parallel across the load confines the current related problems to the load side to make the current from the source purely sinusoidal .
First part of the paper deals with the design and simulation of SRF controlled DSTATCOM based on three-leg and four-leg VSC topology and performance of both is evaluated and compared. Second part deals with the design and simulation of Neural-Network controlled DSTATCOM based on three leg VSC topology. Then the performance of DSTATCOM using both SRF and Neural Network will be compared. For the three-leg voltage-source- converter (VSC) based DSTATCOM configuration a zig-zag transformer is used for neutral current compensation at the PCC.
The current consists of electrons travelling from the n-type region toward the junction, and holes flowing from the p-type region in the opposite direction toward the junction. The two kinds of carriers constantly recombine in the vicinity of the junction. The electrons and holes travel in opposite directions, but have opposite charges, so both contribute to the resulting electric current. Reversing the polarity, making the p-type side (anode) negative negative, the voltage at the cathode becomes higher than at the anode; the diode is working in the reverse bias region. The positive carriers (holes) in the p-type material are pulled away from the junction, causing the width of the depletion zone to increase. Similarly, because the n-type region is now positive, also the electrons will be pulled away from the junction. Thus the voltage barrier over the junction increases, causing an increased resistance to the flow of both kinds of charge carriers, only allowing a small leakage of electric current across the p-n junction.
Fig.3(a) shows the limiting case when Rs/Xs = 1, i.e., θs= 45◦. From (4), the maximum possible load angle is 45◦.The maximum value of angle, θs + φ, can be 135◦ when φ is90◦. Hence, the limiting source current phasor OE, which is denoted by Is limit, will lead the load voltage by 90◦.Lines OC and AB show the limiting vectors of Vs and IsZs, respectively with D as the intersection point. Hence, area under ACDA shows the operating region of DSTATCOM for voltage regulation. The point D has a limiting value of Vs limit= IsZs = 0.706 p.u. Therefore, maximum possible voltage regulation is 29.4%. However, it is impossible to achieve these two limits simultaneously as δ and φ cannot be maximum at the same time. Again if Zs is low then source current, which will be almost inductive, will be enough to be realized by aDSTATCOM.
the pads to the devices via the metal routes and via stacks, there is a voltage drop. This drop must be within certain limit so that the cmos devices are in their correct state of operation. The situation becomes complicated as the switching behavior of the devices change with time depending on the functionality. Different functional modes activate different modules of the design – that are spread over different parts on the frame. Consequently the voltage drops also change. Some regions may now have more voltage drop thereby slowing down the cells while some may have lesser drop thereby fastening the cells – either can cause timing violations if the variations exceed designed limits. Moreover, parasitics in the routes greatly effect these changes causing voltage droops.
Other capacitance based techniques such as Terman method  and quasistatic variants  all have some limitation. Each is limited in accuracy near the band edges, which is again a consequence of the time constants involved at these locations. In the Terman method a “high frequency” capacitance-voltage curve must be measured where interface states cannot respond, but the high frequency condition is not certain to be satisfied since at each bias point the inverse of the trapping time constant must be much smaller than the angular measurement frequency. The problem with higher frequencies is that series resistances become important and they must be deembedded completely before further analysis. In a quasistatic variant it is assumed that capacitance can be measured at such a low frequency that interface states follow completely, but not every device is suitable for low frequencies depending on the device area. This is due to measurement limitations where the detected displacement current is proportional to area, signal amplitude, and frequency. Also, small errors in the oxide capacitance density affect the extraction outcome near the band edges .
The inner cavity containing the amplifying layers is surrounded by electrically conductive layer stacks that form the laser mirrors which provide optical feedback. VCSELs designed for emission wavelengths in the 850 to 980 nm spectral range require about 8 µm of epitaxial grown material, whereas the active region is composed of just a few quantum wells (QWs) with some ten nm thickness. The pin-type doping configuration is similar to conventional edge-emitting lasers (EELs). In the most simple device layouts, electric current is injected from ohmic contacts on the top epitaxial side and the backside of the substrate , . Even though currently some of 980, 850 and 780 nm devices are commercialized into light wave systems, aiming exploring applications, 1300-1550 nm y Usually have small diverging angle, low threshold current and single laser mode output. The structure can be easily
ABSTRACT: A phase lock loop is a closed-loop system that causes one system to track with another. More precisely, a PLL can be perceived as a circuit synchronizing an output signal with a reference or input signal in frequency as well as phase. High-performance phase lock loops are widely used within a digital system for clock generation, timing recovery, and to efficiently sequence operations and synchronize between function units and ICs As the digital system grows the role of phase lock loop increases. Achieving low jitter and phase noise in phase lock loop with less area and power consumption is challenging. The present research relates to characterization and redesign of individual blocks of Phase lock loop (PLL) to improve its characteristics. More specifically redesigning of individual blocks like: Phase Frequency Detector to reduce area and static phase error, Voltage to Current converter to linearly increase the current input to the current controlled oscillator, Current Controlled Oscillator to reduce phase noise, amplitude distortion, area and power consumption. We also introduce an additional feedback loop to increase the gain of the charge pump in a manner that linearizes the overall loop gain over wide bandwidth. The Results are substantial improvements in the PLL characteristics such as low jitter, phase noise, area and power consumption.
The increasing demand of electricity results into overloaded condition of the system. The overloaded condition leads the system to operate in unstable condition. In unstable condition voltages of the buses decreases and can cause voltage collapse . It is a phenomenon that causes severe changes in the power system hence voltage stability analysis becomes necessary. Analysis of voltage stability is also essential from the power system protection point of view [2-3]. Continuation power flow (CPF) is the main analysis tool used for the IEEE 6 and IEEE 30 bus system. CPF technique involves the use of predictor and corrector step for analysing staticvoltage stability . In this paper, for the analysis of staticvoltage stability maximum loading point (MLP) and megawatt margin (MWM) are used. Contingency analysis is important factor while considering the power system protection . Operation of system under no contingency gives maximum loading point and maximum megawatt margin. Continuation power flow method is implemented on IEEE 6 and IEEE 30 bus systems for the computation of MLP and its corresponding decrease in MWM.
AM conceived the studies and coordinated the experiment. All of the authors participated to the analysis of the data and wrote the article. PO, GM and ED carried out the sample preparation and the measurements for elementary semiconductors: Si, Ge.RR carried out the measurements of current – voltage characteristics. All authors read and approved the final manuscript.
Reference  shows the relationship between load characteristic and voltage stability by studying the power exponent relationship between the voltage stability re- gion and the power function model. Reference  ana- lyzes voltage stability with load modeling according to the load characteristic space, which has a very strong generalization capability. However, the generalization capability is not enough for unknown sample space. Ref- erence  investigates the influence of stalling of induc- tion motor to PV curve and voltagestatic stability. However, it doesn’t consider the change of PV curve along with the change of the operating condition. Refer- ence  transforms the induction motor parameters to line parameters and describes load characteristic of in- duction motor with the constant power load model, but it does not take the instable character of induction motor into account. Reference  shows that the adjusting proportion of the dynamic load model will causes the changes of the instable mode by simulation, and there are different effects on the voltage stability under the differ- ent instable mode. Reference  studies the node critical
Current to voltage converter is one of the basic building blocks in analog circuits. Aiming at the needs of wide dynamic range, design of current to voltage conversion circuit is required. A current to voltage conversion can be realized by means of a charge accumulation process. If the time of the charge accumulation is made variable, then the gain of the conversion can be variable. However, this approach requires a linear capacitor and introduces, in many cases, a significant delay. Also, for the variable charge accumulation time, additional circuitry is required, which may add a complexity in the circuit structure. Another approach of the conversion is to use the logarithmic feature of MOS transistors. If the input current flow through a MOS channel and the gate-to-source voltage is made to vary with the current, this voltage will be logarithmically proportional to the current. Althoug this approach provides a variable gain and a wide input signal range, the sensitivity of the circuit is usually low.