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Installieren Sie die genialokal App auf Ihrem Startbildschirm für einen schnellen Zugriff und eine komfortable Nutzung.
Installieren Sie die genialokal App auf Ihrem Startbildschirm für einen schnellen Zugriff und eine komfortable Nutzung.
A custom HFET model was developed and applied in the design of several MMIC applica- tions. The model is expressly dedicated to microwave circuit design. Its analytical nonlinear equations provide a compromise between physical interpretability, numerical efficiency and global validity. As an essential part of the overall model, the COBRA expression features a highly efficient and accurate description of complex HFET drain current characteristics. A modification was introduced to include the reduction of drain current due to the self-heating effect as well as for improved description of gain compression. A new approach to frequency dispersion modelling extends the model’s validity range from the microwave- down to the low-frequency and DC regimes. The proposed dispersion model relies on conventional device characterisation techniques and standard parameter ex- traction procedures. The inclusion of multiple dispersion time constants and exponentially decaying step responses accurately reflects the physical nature of individual dispersion ef- fects, providing a correct description of transitions between dispersion regimes both in the time- and frequency domain. As a consequence, the model allows for accurate assessment of dynamic (gain, matching, intermodulation etc.), static (e.g. biasing, power consumption) as well as combined (e.g. PAE, self-biasing) figures of merit during the design phase. Addition- ally, the simulation error introduced by neglecting frequency dispersion when using purely static or dynamic drain current models, can be evaluated. A unified capacitance model approach defines the frame for sets of charge-conservative expressions for gate capacitance characteristics. The final equations employed here resemble in composition the Curtice IV model, e.g. in terms of transition from linear- to saturated- and from sub-threshold- to active voltage regimes. The universal validity of the model was demonstrated by applying it to several different HEMT technologies, encompassing both state-of-the-art GaAs pHEMT low-noise and power processes, high-frequency InP pHEMTs as well as novel concepts such as the strained-Si/SiGe mHEMT. Both the nonlinear capacitance and dispersion models proved to apply very well to all HEMT technologies.
