In this paper, a new model formulation is presented that correctly accounts for low-frequency dispersion (i.e., trapping and thermal phenomena) affecting field-effect transistors (FETs). In particular, for the first time a behavioral description is applied only to the intrinsic current generator, enabling the correct measurement-based evaluation of the intrinsic device operation. The model, which is by construction technology independent, has been extensively validated considering a GaN FET. This choice is justified by the large interest around this technology and by the presence of dispersion effects that must be accurately accounted for.

A novel methodology for the characterization of the nonlinear dynamic behavior of electron devices (EDs) is presented. It is based on a complete and accurate ED characterization that is provided by large-signal low-frequency I/V measurements, performed by means of a low-cost setup, in conjunction with any model-based description of the nonlinear reactive effects related to ED capacitances. The unique feature of the proposed technique is that a fully harmonic control of waveforms at the current generator plane is achieved, and as a consequence, high-efficiency operation can be simply investigated. Different experimental data are presented on GaAs and GaN transistors, and to definitely verify the capability of the new approach, the design of a class-F GaN power amplifier is deeply investigated as a case study.

In this paper, we apply for the first time the nonlinear-embedding technique to the design of power amplifiers (PAs) based on laterally-diffused metal-oxide-semiconductor (LDMOS) field-effect transistors. Such a design technique is based on setting the transistor load line at the intrinsic current-generator plane, according to well-known theoretical guidelines. Then, the selected operating condition can be transposed at any design frequency at the extrinsic transistor terminals, by means of a model of the device nonidealities, such as the nonlinear intrinsic capacitances and the linear parasitic effects. A harmonically-tuned high-efficiency class-F and a wideband class-AB PAs operating within the FM broadcasting band 88 ÷ 108 MHz based on a 10-W LDMOS are then designed and realized. To definitely assess the validity of the proposed approach for the LDMOS technology, we compare the measured performance on the fabricated PAs with the expected predictions.

GaN FETs have achieved superior performance in the design of microwave power circuits. Nevertheless, the amount of dispersion related to this technology poses severe issues for the correct modeling and characterization of these devices. In this letter, the effects of GaN FET dispersion on the design of power amplifiers (PAs) with dynamic power supply, largely adopted in state-of-the-art high-efficiency pulsed radar transmitters, are discussed. In particular, we propose a technique for evaluating GaN device performance degradation in new-generation PAs that represents an effective alternative to pulsed-RF multiharmonic source/load-pull microwave setups.

The gallium-nitride (GaN) high electron-mobility transistor (HEMT) technology has emerged as an attractive candidate for high-frequency, high-power, and high-temperature applications due to the unique physical characteristics of the GaN material. Over the years, much effort has been spent on measurement-based modeling since accurate models are essential for allowing the use of this advanced transistor technology at its best. The present analysis is focused on the modeling of the scattering (S-) parameter measurements for a 0.25 μm GaN HEMT on silicon carbide (SiC) substrate at extreme operating conditions: a large gate width (i.e., the transistor is based on an interdigitated layout consisting of ten fingers, each with a length of 150 μm, resulting in a total gate periphery of 1.5 mm), a high ambient temperature (i.e., from 35 °C up to 200 °C with a step of 55 °C), a high dissipated power (i.e., 5.1 W at 35 °C), and a high frequency in the millimeter-wave range (i.e., from 200 MHz up to 65 GHz with a step of 200 MHz). Three different modeling approaches are investigated: the equivalent-circuit model, artificial neural networks (ANNs), and gated recurrent units (GRUs). As is shown, each modeling approach has its pros and cons that need to be considered, depending on the target performance and their specifications. This implies that an appropriate selection of the transistor modeling approach should be based on discerning and prioritizing the key features that are indeed the most important for a given application.