Accurate Small-signal Equivalent Circuit Research Articles

Small-Signal Model of an Inductive Power Transfer System Using LCC–LCC Compensation

The LCC–LCC compensation is widely used in the inductive power transfer systems. However, there is no simple and accurate small-signal equivalent circuit model for this resonant converter. Based on the extended describing function method, this article proposed a full-order (17th-order) equivalent circuit model to accurately predict the small-signal behaviors. For simplification, the full-order model is gradually simplified to a ninth-order model and finally to a fifth-order model. The input to output transfer function are analytically derived for the first time. Both simulation and experimental results are presented to justify the effectiveness of the model, and the model is accurate up to one-fifth of the switching frequency.

Equivalent Circuit Modeling of LLC Resonant Converter

LLC resonant converter is widely used in industry. However, up to now, no simple and accurate small-signal equivalent circuit model is available. This article proposes an equivalent circuit model of LLC resonant converter. The simple equivalent circuit model is derived based on modification and simplification of extended describing function method, which has already been successful deriving equivalent circuit model in series resonant converter [15] . The model can well predict the small-signal behaviors observed in pulse-frequency-modulated LLC resonant converter, whenever switching frequency is below, close to, or above the resonant frequency. For the first time, analytical expressions for control to output voltage, input to output voltage, input impedance, and output impedance are provided to aid closed-loop feedback design. SIMPLIS simulation and experimental results are presented to prove the accuracy of the model.

Accurate Small-Signal Equivalent Circuit Modeling of Resonant Tunneling Diodes to 110 GHz

This article presents a novel, on-wafer deembedding technique for the accurate small-signal equivalent circuit modeling of resonant tunneling diodes (RTDs). The approach is applicable to stabilized RTDs, and so enables the modeling of the negative differential resistance (NDR) region of the device’s current–voltage ( $I$ – $V$ ) characteristics. Furthermore, a novel quasi-analytical procedure to determine all the equivalent circuit elements from the deembedded S-parameter data is developed. Extraction results of a $10\,\,\mu \text{m}\,\,\times 10\,\,\mu \text{m}$ stabilized, low-current density RTD at different bias points show excellent fits between modeled and measured S-parameters up to 110 GHz.

Effects of Gate-Length Scaling on Microwave MOSFET Performance

This paper focuses on the extraction of an accurate small-signal equivalent circuit for metal-oxide-semiconductor field-effect transistors (MOSFETs). An analytical modeling approach was developed and successfully validated through the comparison between measured and simulated scattering parameters. The extraction of the equivalent circuit elements allowed for the estimation of the intrinsic unity current-gain cutoff frequency, which is a crucial figure of merit for assessing the high-frequency performance. The experimental data show that the cutoff frequency of the tested devices exhibits a nearly ideal scaling behavior with decreasing gate length.

7.8-GHz flexible thin-film transistors on a low-temperature plastic substrate

RF flexible thin-film transistors (TFTs) with a new speed record of cut-off frequency (fT) of 2.04 GHz and maximum oscillation frequency (fmax) of 7.8 GHz were realized using single-crystal Si nanomembrane as an active channel layer on a low-temperature plastic substrate. We report the detailed device layout design considerations for optimizing the frequency response of the flexible RF TFTs, supported by accurate small-signal equivalent circuit modeling. It is indicated that, by properly considering the tradeoff between the parasitic source/drain resistances and the parasitic source-to-gate/drain-to-gate capacitances, fT and fmax of the single-crystal-Si TFTs can be optimized separately in order to meet the requirements of certain potential RF applications.

Accurate Multibias Equivalent-Circuit Extraction for GaN HEMTs

This paper focuses on the determination and analysis of an accurate small-signal equivalent circuit for gallium-nitride high electron-mobility transistors under different bias conditions. Our experimental results show that a channel capacitance has to be added to the conventional forward "cold" model for modeling the device-under-test. The validity of the proposed extraction procedure has been verified by the very good agreement between simulated and measured scattering parameters up to 50 GHz

Extraction of small-signal model parameters of silicon MOSFET for RF applications

An efficient, direct method to extract the admittance parameters and an accurate small-signal equivalent circuit model of an MOS transistor for RF applications have been developed, incorporating the effect of the channel-length modulation. The Y-parameter expressions are developed in terms of MOSFET parameters, parasitic elements, frequency, and bias conditions. Further, the scattering parameters and different gains for an Si–MOSFET have been evaluated to show its RF behavior. The results obtained are compared with experimental data, and are in good agreement. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 352–358, 2000.