TFT Small Signal Model and Analysis

We present an accurate small signal model for thin film transistors (TFTs) taking into account non-idealities such as contact resistance, parasitic capacitance, and threshold voltage shift. The model gives high accuracy in s-parameters, and the predicted cutoff frequency yields 1% discrepancy compared with measurement results. In contrast, the conventional CMOS small signal model adapted for TFTs yields 12.5% error. The TFT’s cutoff frequency is also evaluated under bias stress to examine the effect of device instability on small signal behavior.This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/LED.2016.257592

Small Signal Model Averaging of Bi-Directional Converter

We consider the problem of modeling a bi-directional AC/DC converter using a small signal approach coupled with cycle averaging to simplify the model for use in digitized control. Small power sources (less than or equal to 1000W) tend to have more abrupt transient power flow due to the associated characteristic low inertia. This is prevalent in small wind turbine systems. In an effort to reduce the complexity of system control under fast power transients, we develop an averaged model which allows for more advanced controller design while keeping computations reasonable low. This effort is intended to complement related work in distributed generation power flow measurement and control suitable for emerging smart-grid and micro-grid systems. We also utilize a more accurate inductor model incorporating resistive effects for the converter power coupling device. Simulation results are provided demonstrating the capability of the model

Small-signal model for saturated deep-bar induction machines

A small-signal model is presented for saturated deep-bar induction machines. Inductances are allowed to saturate as a function of their own current (or flux), and the mutual saturation effect originating mainly from closed or skewed rotor slots is also included in the model. The model fulfills the reciprocity conditions, and it can applied to parameter estimation and to the analysis and development of flux angle estimation methods. The model is applied to estimating the parameters of a 37-kW deep-bar cage-induction machine, using the data from time-stepping finite-element analysis (FEA). The proposed model fits very well to the FEA data in a wide frequency range.Peer reviewe

Design of carbon nanotube field effect transistor (CNTFET) small signal model

The progress of Carbon Nanotube Field Effect Transistor (CNTFET) devices has facilitated the trimness of mobile phones, computers and all other electronic devices. CNTFET devices contribute to model these electronics instruments that require designing the devices. This research consists of the design and verification of the CNTFET device's small signal model. Scattering parameters (S-parameters) is extracted from the CNTFET model to construct equivalent small model circuit. Current sources, capacitors and resistors are involved to evaluate this equivalent circuit. S-parameters and small signal models are elaborated to analyze using a technique to form the small signal equivalent circuit model. In this design modeling process, at first intrinsic device's Y-parameters are determined. After that series of impedances are calculated. At last, Y-parameters model are transformed to add parasitic capacitances. The analysis result shows the acquiring high frequency performances are obtained from this equivalent circuit

Frequency Response of Graphene Electrolyte-Gated Field-Effect Transistors

This work develops the first frequency-dependent small-signal model for graphene electrolyte-gated field-effect transistors (EGFETs). Graphene EGFETs are microfabricated to measure intrinsic voltage gain, frequency response, and to develop a frequency-dependent small-signal model. The transfer function of the graphene EGFET small-signal model is found to contain a unique pole due to a resistive element, which stems from electrolyte gating. Intrinsic voltage gain, cutoff frequency, and transition frequency for the microfabricated graphene EGFETs are approximately 3.1 V/V, 1.9 kHz, and 6.9 kHz, respectively. This work marks a critical step in the development of high-speed chemical and biological sensors using graphene EGFETs.United States. Office of Naval Research (Grant N00014-12-1-0959)United States. Office of Naval Research (Grant N0014-16-1-2230)United States. National Aeronautics and Space Administration (Award NNX14AH11A)United States. Army Research Office (Contract W911NF-13-D-0001

Small-signal model for 2D-material based field-effect transistors targeting radio-frequency applications: the importance of considering non-reciprocal capacitances

A small-signal equivalent circuit of 2D-material based field-effect transistors is presented. Charge conservation and non-reciprocal capacitances have been assumed so the model can be used to make reliable predictions at both device and circuit levels. In this context, explicit and exact analytical expressions of the main radio-frequency figures of merit of these devices are given. Moreover, a direct parameter extraction methodology is provided based on S-parameter measurements. In addition to the intrinsic capacitances, transconductance and output conductance, our approach allows extracting the series combination of drain/source metal contact and access resistances. Accounting for these extrinsic resistances is of upmost importance when dealing with low dimensional field-effect transistors.Comment: 8 pages, 10 figures, 4 table

Microwave characteristics of GaAs MMIC integratable optical detectors

Interdigitated photoconductive detectors were fabricated on microwave device structures, making them easily integratable with Monolithic Microwave Integrated Circuits (MMIC). Detector responsivity as high as 2.5 A/W and an external quantum efficiency of 3.81 were measured. Response speed was nearly independent of electrode geometry, and all detectors had usable response at frequencies to 6 GHz. A small signal model of the detectors based on microwave measurements was also developed