Measurement-based Investigation of the DC and RF Transconductance for Various HEMT Technologies in High-and Low-temperature Conditions

The purpose of this experimental study is to evaluate quantitatively the impact of the temperature on the behavior of various high electron-mobility transistor (HEMT) technologies through the analysis of the DC and RF transconductance. The experimental data are reported for six different HEMT devices, in order to develop a comparative analysis based on various technologies, including gallium arsenide (GaAs) and gallium nitride (GaN) materials, matched and pseudomorphic HEMTs, single- (S-H) and double-heterojunction (D-H) HEMTs, and both virgin and multi-layer devices. The reported findings show that the impact of the ambient temperature on the HEMT behavior strongly depend on the tested technology and operating conditions. As a matter of fact, a higher temperature can lead to increased or degraded transconductance, depending on the device technologies and bias point. In the GaAs-based devices, an operating bias condition at which the DC and RF transconductance are temperature insensitive can be defined, owing to two-opposite temperature-dependent effects counteracting with each other.

Temperature-Sensitivity of Two Microwave HEMT Devices: AlGaAs/GaAs vs. AlGaN/GaN Heterostructures

The goal of this paper is to provide a comparative analysis of the thermal impact on the microwave performance of high electron-mobility transistors (HEMTs) based on GaAs and GaN technologies. To accomplish this challenging goal, the relative sensitivity of the microwave performance to changes in the ambient temperature is determined by using scattering parameter measurements and the corresponding equivalent-circuit models. The studied devices are two HEMTs with the same gate width of 200 µm but fabricated using different semiconductor materials: GaAs and GaN technologies. The investigation is performed under both cooled and heated conditions, by varying the temperature from −40 °C to 150 °C. Although the impact of the temperature strongly depends on the selected operating condition, the bias point is chosen in order to enable, as much as possible, a fair comparison between the two different technologies. As will be shown, quite similar trends are observed for the two different technologies, but the impact of the temperature is more pronounced in the GaN device.

A Lossy Integrator with Active Bias Point

A lossy integrator with active bias point<br>

A Lossy Integrator with Active Bias Point

A lossy integrator with active bias point<br>

Evidence of Strange Attractors in Class C Amplifier with Single Bipolar Transistor: Polynomial and Piecewise-Linear Case

This paper presents and briefly discusses recent observations of dynamics associated with isolated generalized bipolar transistor cells. A mathematical model of this simple system is considered on the highest level of abstraction such that it comprises many different network topologies. The key property of the analyzed structure is its bias point since the transistor is modeled via two-port admittance parameters. A necessary but not sufficient condition for the evolution of autonomous complex behavior is the nonlinear bilateral nature of the transistor with arbitrary reason that causes this effect. It is proved both by numerical analysis and experimental measurement that chaotic motion is miscellaneous, robust, and it is neither numerical artifact nor long transient motion.