Showing papers on "NQS published in 2003"

Quasi-static and nonquasi-static compact MOSFET models based on symmetric linearization of the bulk and inversion charges

Abstract: A particularly simple form of the charge-sheet model (CSM) is developed using symmetric linearization of the bulk charge as a function of the surface potential. The new formulation is verified by comparison with the original form of the CSM and is used to obtain a simple and accurate expressions for the quasi-static (QS) terminal charges based on the Ward-Dutton partition. Combined with the spline collocation version of the weighted residuals method, symmetric linearization leads to a relatively simple version of the nonquasi-static (NQS) MOSFET model. The efficiency of the proposed approach to MOSFET modeling is enhanced by taking advantage of the recently developed noniterative algorithm for computing surface potential as a function of the terminal voltages. An important symmetry of the various MOSFET characteristics with respect to the source/drain interchange is preserved in both the QS and NQS versions of the symmetrically linearized CSM.

A new approach to model nonquasi-static (NQS) effects for MOSFETs. Part II: Small-signal analysis

Abstract: We present a new approach to model nonquasi-static (NQS) effects in a MOSFET in a small-signal situation. The model derived here is based on the large-signal NQS model previously proposed. The derivation of the small-signal model is presented. The small-signal parameters obtained with this model prove to be accurate up to very high frequencies. An excellent match between the new model and device simulation results has been observed even when the frequency is many times larger than the cutoff frequency.

Non-Quasi-Static (NQS) Thermal Noise Modeling of the MOS Transistor

Abstract: This paper presents a non-quasi-static (NQS) thermal noise model of the MOS transistor that is valid in all modes of operation, from weak to strong inversion, and up to frequencies which are near or above the NQS cut-off frequency. It is shown that in addition to the well-known induced gate noise (IGN) there is also an induced substrate noise that is generated and that the source and drain noises are also affected. All prior publications on the subject only deal with IGN in strong inversion regime. It is shown that significant differences are obtained for moderate and weak inversion operation. The paper starts with a brief review of NQS model valid in all modes of operation. It then presents a general thermal noise model using four noisy current sources. The power spectral and cross power spectral densities of these noise sources are computed. A first-order approximation is then derived and compared to the complete model. Noise excess factors for the drain and the gate noise are then calculated and the correlation coefficient between the drain and the gate noise is obtained. It is shown that this correlation factor is always null in conduction (VD = VS), and varies in saturation between j0.6 in weak inversion to j0.4 in strong inversion. To our knowledge, it is the first time that a complete HF thermal noise model of the MOST is presented, that is valid in all modes of inversion and up to and above the NQS cut-off frequency.

A Self-Consistent Non-Quasi-Static MOSFET Model for Circuit Simulation Based on Transient Carrier Response

Abstract: We have developed a basic concept for a non-quasi-static (NQS) metal-oxide-semiconductor field-effect transistor (MOSFET) model for circuit simulation. The model is based on a carrier-response delay, and incorporates the time and position dependence of the carrier density along the channel. This is the exact origin of the NQS effect. By comparing model results with 2D device simulation results, solving the continuity equation explicitly, we found that the carrier-response delay consisted of a conductive delay and a charging delay. The developed model was successfully applied to test transient behavior of the drain current.

Implementation of nonquasi-static effects in compact bipolar transistor models

Abstract: Large-signal implementation of nonquasi-static (NQS) effects in bipolar transistors is reviewed. An approach is proposed to introduce first-order NQS correction to typical quasi-static phenomenological models. Both charge- and noncharge-conserving implementations are considered. The resulted large-signal equivalent-circuit model compares well with the two-dimensional physical model in simulating HBT transient response under high-current operations. The present approach advances the state-of-the-art by allowing arbitrary bias dependence of transit times in large-signal NQS models.

Effect of scaling on the non-quasi-static behaviour of the MOSFET for RF ICs

Abstract: The effect of scaling (1 /spl mu/m to 0.09 /spl mu/m) on the non-quasi-static (NQS) behaviour of the MOSFET has been studied using process and device simulation. It is shown that under fixed gate (V/sub gs/) and drain (V/sub ds/) bias voltages, the NQS transition frequency (f/sub NQS/) scales as 1/L/sub eff/ rather than 1/L/sup 2//sub eff/ due to the velocity saturation effect. However, under the practical scaling guidelines, considering the scaling of supply voltage as well, f/sub NQS/ shows a turn around effect at the sub 100 nm regime. The relation between unity gain frequency (f/sub t/) and f/sub NQS/ is also evaluated and it is shown that f/sub t/ and f/sub NQS/ have similar trends with scaling.

A non-quasi-static small-signal MOSFET model for radio and microwave frequencies including spreading gate resistances and capacitances

Abstract: A new physically consistent, fully analytical non-quasi-static (NQS) small-signal MOSFET model for analysis and simulation of radio and microwave frequency circuits is proposed. Some results of a 3D analysis of spreading gate resistances and capacitances, main features and experimental verification of the new NQS four-terminal model are presented in this report. The validity of this model is experimentally proved up to 27 GHz.

Accurate small-signal model and its parameter extraction in RF silicon MOSFETs

Abstract: An accurate method to extract a small signal equivalent circuit model of RF silicon MOSFETs is presented Analytical calculations are used for each intrinsic parameter and accuracy is within 1% for the entire operational region 2D physical device simulation is used to analyze this methodology A simple non-quasi static (NQS) model is reported, which offers good accuracy needed for circuit simulation, including a simple network representing the coupling between source and drain Accurate extraction methods for extrinsic parameters have been also developed The compact model and its parameter extraction are verified on Si-MOSFETs through S-parameter measurements

Implementation of NQS effects in large-signal BJT models

Abstract: Large-signal implementation of non-quasistatic (NQS) effects in bipolar transistors is reviewed. An approach strategy is proposed that allows bilateral translation between small- and large-signal equivalent circuits. The approach is illustrated by translating simple small-signal equations commonly used in BJT modeling, as well as more complicated ones proposed in the literature. The present approach extends the state of art by considering arbitrary bias dependence of small-signal time constants.