Showing papers on "NQS published in 2006"

A Carrier-Transit-Delay-Based Nonquasi-Static MOSFET Model for Circuit Simulation and Its Application to Harmonic Distortion Analysis

Abstract: In this paper, a compact model of nonquasi-static (NQS) carrier-transport effects in MOSFETs is reported, which takes into account the carrier-response delay to form the channel. The NQS model, as implemented in the surface-potential-based MOSFET Hiroshima University STARC IGFET model, is verified to predict the correct transient terminal currents and to achieve a stable circuit simulation. Simulation results show that the NQS model can even reduce the circuit simulation time in some cases due to the elimination of unphysical overshoot peaks normally calculated by a QS-model. An average additional computational cost of only 3% is demonstrated for common test circuits. Furthermore, harmonic distortion characteristics are investigated using the developed NQS model. While the distortion characteristics at low drain bias and low switching frequency are determined mainly by carrier mobility, distortion characteristics at high frequency are found to be strongly influenced by channel charging/discharging

Studies on photoinduced H-atom and electron transfer reactions of o-naphthoquinones by laser flash photolysis.

Abstract: The quenching of the triplets of 1,2-naphthoquinone (NQ) and 1,2-naphthoquinone-4-sulfonic acid sodium salt (NQS) by various electron and H-atom donors was investigated by laser flash photolysis measurement in acetonitrile and benzene. The results showed that the reactivities and configurations of 3NQ* (3NQS*) are governed by solvent polarity. All the quenching rate constants (kq) measured in benzene are larger than those in acetonitrile. The SO3Na substituent at the C-4 position of NQS makes 3NQS* more reactive than 3NQ* in electron/H-atom transfer reactions. Large differences of kq values were discovered in H-atom transfer reactions for alcohols and phenols, which can be explained by different H-abstraction mechanisms. Detection of radical cations of amines/anilines in time-resolved transient absorption spectra confirms an electron transfer mechanism. Triplets are identified as precursors of formed radical anions of NQ and NQS in photoinduced reactions. The dependence of electron transfer rate constants...

A Unified Nonquasi-Static MOSFET Model for Large-Signal and Small-Signal Simulations

Abstract: The spline collocation-based nonquasi-static (NQS) model is further developed to include all regions of operation and small-geometry effects. The new formulation provides a unified (hence consistent) approach to both large-signal and small-signal NQS modeling and is sufficiently flexible to work with any surface-potential-based MOSFET model. The model is verified through comparison with the channel segmentation method, two-dimensional numerical simulations, and experimental results and demonstrates a controlled tradeoff between model accuracy and efficiency. The new NQS model has been implemented into PSP model. Circuit simulations are given to demonstrate the accuracy and applicability of the new model

Neural Query System: Data-mining from within the NEURON simulator.

Abstract: We have developed a simulation tool within the NEURON simulator to assist in organization, verification, and analysis of simulations. This tool, denominated Neural Query System (NQS), provides a relational database system, a query function based on the SELECT function of Structured Query Language, and data-mining tools. We show how NQS can be used to organize, manage, verify, and visualize parameters for both single cell and network simulations. We demonstrate an additional use of NQS to organize simulation output and relate outputs to parameters in a network model. The NQS software package is available at http://senselab. med.yale.edu/senselab/SimToolDB.

Tagging of Model Amphetamines with Sodium 1,2‐Naphthoquinone‐4‐sulfonate: Application to the Indirect Electrochemical Detection of Amphetamines in Oral (Saliva) Fluid

Abstract: Proof-of-concept is shown for the indirect electrochemical detection of model amphetamines, D-amphetamine sulfate and pseudoephedrine, based on the labeling of the amphetamine models with sodium 1,2-naphthoquinone-4-sulfonate (NQS). The presence of the amphetamine models is monitored via either the reduction in the magnitude of the voltammetric peak corresponding to the electrochemical reduction of the quinone functionality of the sodium 1,2-naphthoquinone-4-sulfonate or via growth of a new voltammetric peak related to reaction between the amphetamine model and NQS, both of which are well resolved from one another. The protocol is shown to be successful in artificial saliva and authentic human oral (saliva) fluid. Such a protocol may be particularly attractive for roadside testing of amphetamines in drug drivers.

Determination and Validation of an LC Method for Fluvoxamine in Tablets

Abstract: A new, simple, rapid and specific reversed-phase high-performance liquid chromatography (HPLC) method was developed and validated for the determination of fluvoxamine in pharmaceutical dosage forms. The HPLC separation was achieved on a C18 μ-Bondapack column (250 mm × 4.6 mm) using a mobile phase of acetonitrile–water (80:20, v/v) at a flow rate of 1 mL min−1. Proposed method is based on the derivatization of fluvoxamine with 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS) in borate buffer of pH 8.5 to yield a orange product. The HPLC method is based on measurement of the derivatized product using UV-visible absorbance detection at 450 nm. The method was validated for specificity, linearity, precision, accuracy, robustness. The degree of linearity of the calibration curves, the percent recoveries of fluvoxamine, the limit of detection and quantification, for the HPLC method were determined. The assay was linear over the concentration range of 45–145 ng mL−1 (r = 0.9999). Limit of detection and quantification for fluvoxamine were 15 and 50 ng mL−1, respectively. The results of the developed procedure (proposed method) for fluvoxamine content in tablets were compared with those by the official method. The method was found to be simple, specific, precise, accurate, reproducible and robust.

Compact Modeling of Anomalous High-Frequency Behavior of MOSFET's Small-Signal NQS Parameters in Presence of Velocity Saturation

Abstract: This paper presents a physical charge-based compact small-signal nonquasi-static (NQS) model for MOST, including velocity saturation and valid in all regions of inversion (from weak to strong inversion). This model intrinsically predicts the anomalous high-frequency behavior of transadmittance (ydg) in saturation, which was observed earlier in both device simulation and measurement. It also shows that the inclusion of velocity saturation causes the magnitude of the gate-to-drain admittance ydg to start to increase (instead of decreasing) above a certain frequency and its real part also starts to increase in the negative direction instead of becoming zero. In addition, even for a long channel MOST, the weak inversion charge present at the drain can also affect the ydg in a similar way

Visible Spectrophotometric Methods For The Determination Of Rizatriptan In Pure Form And In Pharmaceutical Formulations

Abstract: Three simple spectrophotometric methods (A, B and C) are described for the determination of rizatriptan (RZT) in pure form and in pharmaceutical formulations. Method A is based on the oxidative coupling reaction between RZT with 2, 6- dichloroquinone - 4 -chlorimide (DCQC) and the color developed was measured at 610 nm. Method B is based on the replacement of sulfonate group of 1, 2 - napthoquinone - 4- sulphonic acid (NQS) by an imino group of indole moiety of RZT producing a colored product which absorbs maximally at 480 nm. Method C is based on the oxidative coupling reaction between RZT and brucine in presence of sodium metaperiodate and the color developed was measured at 530 nm. The optimum experimental parameters for the color production are selected. Beer’s law is valid with in a concentration range of 5.0 - 25.0 μg/ml for method A, 15-75 μg/ml for method B and 8 -40 μg/ml for method C. The results obtained are reproducible and are statistically validated and found to be suitable for the assay of RZT in pharmaceutical formulations.

Modeling of anomalous frequency and bias dependences of effective gate resistance in RF CMOS

Abstract: This paper explains the frequency and bias dependences of the effective gate resistance (real part of h11) by considering the effect of the gate-to-body capacitance, gate-to-source/drain overlap capacitances, fringing capacitances, and nonquasi-static (NQS) effect. A new method of separating the physical gate resistance and the NQS channel resistance is proposed. Separating the gate-to-source parasitic capacitances from the gate-to-source inversion capacitance is found to be necessary for an accurate modeling of all the Y-parameters

Halo Doping: Physical Effects and Compact Modeling

Abstract: In this paper, we present the physical effects observed when halo implants are used to control short channel effects (SCE). The impact of using halo implants was studied using a 2 or 3 segmented transistor. The multi-segmented transistor model approach show that (1) the mobility needed to match IV data shows an artificial length dependence, (2) the threshold voltage needed to match the IV data is different from the threshold voltage needed to match CV data and (3) the NQS effects are more severe for halo transistors. Two dimensional numerical devices simulations were also performed to comprehend the observed output resistance degradation. Based on these numerical simulations a 2-transistor model is proposed to describe output resistance in compact models.

Modelling of strained-Si/SiGe NMOS transistors including DC self-heating

Abstract: In this paper, a new model of surface-channel strained-Si/SiGe NMOSFETs is derived based on the extension of non-quasi-static (NQS) circuit model developed previously for bulk-Si devices Basic equations of the NQS MOS model have been modified to account for new physical parameters of strained-Si and relaxed-SiGe layers In addition, the device steady-state self-heating is efficiently included without employing the thermal-flow analog auxiliary sub-circuits From the comparisons of modelling results with numerical simulations and measurements, it is shown that a modified NQS MOS including steady-state self-heating can accurately predict the DC characteristics of strained-Si/SiGe NMOSFETs

Active and Passive RF Device Compact Modeling in CMOS Technoloies

Abstract: A new method for extracting ?-type substrate resistance model of RF MOSFETs based on 3-port measurement is presented. Using NQS and macro-model with extracted substrate components, it is verified that the new substrate resistance model is accurate. Also, temperature dependent macro model is developed. An analytical high frequency thermal noise model for short-channel MOSFETs which covers all operating regions is developed. A simple wide-band model for on-chip inductors on silicon is presented. Finally, an RF model of an accumulation-mode MOS varactor is presented.

Evaluation of non-quasi-static effects during SEU in deep-submicron MOS devices and circuits

Abstract: In this paper, for the first time, we analyze non-quasi-static (NQS) effects during single-event upsets (SEUs) in deep-submicron (DSM) MOS devices, using extensive 2D device, BSIM4 and look-up table (LUT) simulations. We know that even for DSM transistors and circuits, the quasi-static approximation is valid for most digital applications. However, a single-event particle strike in a memory cell is capable of causing NQS effects which can result in erroneous logic-state prediction. The anomalous effect is attributed to the fast-varying transient (produced during particle-strike), which is able to initiate NQS effects in the transistors of the memory cell. Thus, it becomes important for a circuit designer to incorporate NQS effects during SEU simulation.

NQS effects on MOSFET's terminal currents

Abstract: Channel segments approach is used to investigate NQS (non-quasi-static) effect on MOSFET's behavior. For the first time, NQS effect on terminal currents is examined in addition to channel charge. It is demonstrated that conventional analysis and modeling approach for NQS effect, which only takes into consideration the NQS effect on channel charge, is not sufficient. Both channel charge variation and terminal current variation under NQS working mode need to be included in NQS models for accurate prediction of device behavior. It is found that NQS effect is more significant in saturation region than that in linear region

Analysis and Modeling of NQS Effects in MOSFET’s

Abstract: Three issues regarding NQS effect in MOSFET's are investigated: starting point at which NQS effect be comes significant, NQS effect on channel charge partition , a d NQS model implementation in advanced MOSFET models (PSP, Hisim2 and Bsim4). The starting point of NQS is found to be consistent with device current unit-gai n frequency (ft). It is found that almost no charge i s partitioned to drain side in saturation region at v ery high frequency. Three NQS implementation approaches are compared includinginternal node approach, hidden st ate approach and Spline correlation approach. It is pro ved that the intenal node appraoch and hidden states approac h are theoretically equivalent.

Flexible Polymer Thin-Film Transistor Device Structures And Processes For 13.56 MHz RF Rectifier Circuits

Abstract: Polymeric thin-film transistors (TFTs) have been proposed for several applications including displays, electronic paper, chemical sensors, and radio-frequency identification (RFID) tags. One important technical hurdle that has to be overcome for using organic transistors in RFID tags is for these devices to operate at RF frequencies (typically 13.56 MHz) in the front end. It was long thought that conjugated polymer transistors are too slow for this. In this presentation we will demonstrate that polymer transistor based full-wave rectifier circuits utilizing a polythiophene, a p-channel semiconductor, can operate at this frequency with a useful efficiency. In order to achieve such high-frequency operation, we make use of the non-quasi static (NQS) state of the transistors. Bottom gate and top gate structures are explored and a comparison is made between the observed electrical properties. These circuits are fabricated on PEN (polyethylenenapthalate) or PET (polyethylene-terepthalate) substrates using a spin on dielectric. Gate, source and drain contacts are defined photolithographically using evaporated gold as the metal. Field-effect mobilities in the range of 0.02 and 0.2 cm2/Vs that equal or exceed the highest reported among the ones employing similar geometries on plastic substrates are easily obtained in these systems. In order for NQS based rectification to take place the carrier velocity in a 2 micrometer channel length device needs to be more than 2×104 cm/s. This would correspond to a mobility of 0.1cm2/V-s at a field of 105 V/cm. The rectifiers were based on a 4-transistor full-wave design. A coil (transformer secondary) drives the AC inputs in differential mode. The lower diode connected transistors in a manner similar to the half-wave rectifier define the DC voltage level of the two AC input signals. The two upper transistors are connected as switches and are used to move current from the AC inputs to the positive DC output. The capacitor is used to hold the peak voltage level supplied by the coil through the switch-connected devices. The voltage rectification efficiency is relatively high being as much as 45% at 13.56 MHz. This is among the fastest polymer transistor circuit of any kind demonstrated to date.

A new non-quasi-static non-linear MOSFET model based on physical analysis

Abstract: This paper presents a novel approach to the physical modelling of Si based sub-micron MOSFETs The model is based on a set of simplified transport equations for the conducting channel in a MOSFET These equations incorporate non-quasi-static (NQS) effects due to the inclusion of time derivatives, and describe the semiconductor dynamics in terms of coupled particle and displacement currents leading to a description in terms of a relatively small number of nonlinear differential equations Thus, internal device behaviour can be accurately modelled A new method of modelling the charge density in the channel has also been developed in the form of a single expression that describes the charge under the gate for any biasing conditions The new model has a low empirical content, and is fully continuous over all operating regions