Showing papers on "NQS published in 2005"

Determination of histamine in wines with an on-line pre-column flow derivatization system coupled to high performance liquid chromatography.

Abstract: A new rapid and sensitive high performance liquid chromatography (HPLC) method for determining histamine in red wine samples, based on continuous flow derivatization with 1,2-naphthoquinone-4-sulfonate (NQS), is proposed. In this system, samples are derivatized on-line in a three-channel flow manifold for reagent, buffer and sample. The reaction takes place in a PTFE coil heated at 80 °C and with a residence time of 2.9 min. The reaction mixture is injected directly into the chromatographic system, where the histamine derivative is separated from other aminated compounds present in the wine matrix in less than ten minutes. The HPLC procedure involves a C18 column, a binary gradient of 2% acetic acid-methanol as a mobile phase, and UV detection at 305 nm. Analytical parameters of the method are evaluated using red wine samples. The linear range is up to 66.7 mg L−1 (r = 0.9999), the precision (RSD) is 3%, the detection limit is 0.22 mg L−1, and the average histamine recovery is 101.5% ± 6.7%. Commercial red wines from different Spanish regions are analyzed with the proposed method.

Unified non-quasi-static MOSFET model for large-signal and small-signal simulations

Abstract: The spline-collocation-based non-quasi-static model is extended to include small-geometry effects and to enable both small-signal and large-signal simulations. The new NQS model has been implemented into circuit simulators using both SP and PSP models and verified using RF test data. Additional verification is provided by comparison with the results of numerical simulations and with the MM11 channel segmentation method. The large-signal and small-signal simulation results are compatible and consistent with the quasi-static formulation at low frequencies

13.56 MHz organic transistor based rectifier circuits for RFID tags

Abstract: One of the potential application areas for organic and polymers transistors is in radiofrequency identification (RFID) tags. One of the key components of an RFID tag is the front-end rectifier that must rectify a 13.56 MHz AC signal received from a resonant tuned antenna. The rectifier supplies operating power to the tag. Organic transistor circuits have hitherto not operated at this high frequency. We show that by operating pentacene transistors in the non-quasi-static (NQS) regime such operating speeds can be achieved in rectifier circuits. The circuits were fabricated on flexible plastic substrates and employed a solution-cast dielectric. The pentacene mobilities are in the range 0.1-1.5 cm2/V-s. The channel lengths of the transistors are in the range 2-4 μm. Full-wave NQS mode rectifiers were measured to have voltage rectification efficiency in excess of 28% at 14 MHz, demonstrating that such circuits can be used in RFID tags. These circuits operated successfully at speeds up to 20 MHz.

A compact nonquasi-static MOSFET model based on the equivalent nonlinear transmission line

Abstract: A compact physics-based nonquasi-static (NQS) metal-oxide-semiconductor field-effect transistor (MOSFET) model with the equivalent nonlinear transmission line (TL) representing channel carriers drift-diffusion transport is developed and implemented in the simulation program with integrated circuit emphasis (SPICE) program. An auxiliary subcircuit is described, which efficiently solves the channel surface boundary potentials without the need for employing separate iterative algorithms. The short-channel effects and the quantum effects are efficiently included owning to a surface-potential-based modeling approach. In comparison with other Berkeley short-channel IGFET model 3 (BSIM3)-based NQS MOSFET models, it is shown that the new NQS TL model has the advantages in higher accuracy and substantially fewer number of model parameters. From comparison with a two-dimensional device simulator, it is demonstrated that the new NQS TL model can accurately predict dc, ac, and transient behavior of long- and short-channel n-type MOSFETs in all operational regions and for the input signal frequencies up to 10 f/sub T/ values, using only one set of model parameters.

Non-quasi-static physics-based circuit model of fully-depleted double-gate SOI MOSFET

Abstract: In this paper, we describe a compact non-quasi-static (NQS) model of fully-depleted (FD) double-gate (DG) SOI MOSFETs developed on the modified NQS model for bulk single-gate devices. Based on the comparison with the 2-D numerical device simulations, it is shown that new NQS model can accurately predict dc, ac and transient characteristics of FD DG MOSFETs in all operational regions and for small-signal frequencies up to a few cut-off frequencies.

Compact modeling of anomalous high frequency behavior of MOSFET's small-signal NQS parameters in presence of velocity saturation

Abstract: In this work we present a physics based compact small-signal nonquasi static (NQS) model for MOST including velocity saturation and demonstrate that this can substantially change the behavior of the gate transadmittance (y/sub dg/) in saturation at high frequency. The magnitude of y/sub d/g starts to increase (instead of decreasing) after a certain frequency and its real part also starts to increase in negative direction instead of becoming zero. In addition, even for a long channel MOST, the weak inversion charge present at the drain can also effect the y/sub dg/ in a similar way.

Input non-quasi-static effect in SiGe HBTs and its impact on noise modeling

Abstract: The input non-quasi-static (NQS) effects in SiGe HBTs are analyzed using Taylor series expansions of intrinsic Y-parameter expressions. The input NQS effect is shown to strongly affect extraction of the intrinsic base resistance and hence NF/sub min/ modeling.

Flow-Injection Differential Spectrophotometric pH Selectivity System for the Determination of Cyclamate Contaminants

Abstract: A flow-injection system with differential spectrophotometric detection is proposed for the simultaneous determination of aniline and cyclohexylamine based on their reaction with 1,2-naphthoquinone-4-sulfonate (NQS). The pH is chosen to achieve selectivity since only aniline reacts at acidic pH whereas the two amines are derivatized in basic medium. The flow manifold comprises two reactors and two detection cells for developing and monitoring the reaction under selective and general (non-selective) conditions. A double beam spectrophotometer is used for differential detection, with two flow cells placed in the sample and reference holders. Figures of merit such as sensitivity, linear range, detection limit and precision are established. The evaluation of accuracy using a series of synthetic mixtures indicates overall prediction errors of 3% and 5% for aniline and cyclohexylamine, respectively. The method is applied to the determination of amine impurities in commercial sweeteners. Good concordance between the proposed and the standard chromatographic methods is found.

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.

A New Non-Quasi Static Mosfet Model

Abstract: Recent progress in wireless communication is sustained through integrated circuit technologies that offer a low cost and low power devices that operate in the Radio Frequency (RF) range with relatively low noise figure. The submicrometer CMOS technology presents a serious alternative to the more expensive, high power GaAs and Si bipolar technologies that have been used for the design of high frequency ICs. Design testing and verification through circuit simulation is a critical step in the design cycle of RF integrated circuits (RFICs). Accurate device models are therefore required to reduce design cycles and to achieve success when the circuit is finally committed to silicon.This thesis addresses the Radio Frequency (RF) small-signal and large-signal models for the MOS transistor. The quasi-static (QS) and non-quasi-static (NQS) models are discussed and the assumptions used in their development are examined. The various charge components are briefly introduced and the source/drain charge partitioning is presented. The limitation of the QS approach at high frequency is investigated using the Bsim3v3.1 model. The development of a first order NQS small-signal model is briefly presented and its suitability for RF applications is indicated. The effect of the distributed gate, channel, and substrate resistances on the high frequency characteristics of the MOS transistor is examined. We propose a Radio Frequency small-signal equivalent circuit (EC) together with an efficient parameter extraction algorithm that is necessary for the device optimization and the development of accurate large-signal models. The validity of the proposed model and the accuracy of the extraction method are verified by comparing Pspice simulation results of the EC to experimental data and the Bsim3v3.1 model up to 10GHz.