In the 900-MHz to 2.4-GHz spectrum, power-amplifier designers are reaping the benefits of recent advances in silicon-based lateral-diffused MOS (LDMOS) power transistors. And this was evident at this week’s IEEE International Microwave Symposium in Fort Worth, Texas, where proponents disclosed new introductions with significant improvements over previous generation. These include Advanced Power Technology RF (APT-RF), Cree Microwave, and Freescale Semiconductor, formerly Motorola Semiconductor.

APT-RF, for instance, unwrapped a 32 V LDMOS FET capable of providing 300 W(peak) from 1030 to 1090 MHz. Aimed at next-generation avionics applications, the 1011LD300 is nitride passivated and uses gold metallization to achieve high MTTF. Likewise, Cree Microwave also disclosed a linear pulse power LDMOS transistor for Mode-S and TCAS applications. With high gain and better-than 20 dB dynamic range provided by UGF1011-300S, the system design is simplified. In addition, inherent linearity of the device eliminates signal-filtering requirements. The UGF1011-300S is also rated for 300 W peak output power.

Additionally, Cree Microwave also released a library of accurate and scalable non-linear models for its LDMOS power transistors. The models are based on a new Cree-Modelithics-Curtice (CMC) model, developed in collaboration among Cree Microwave, Modelithics, and W.R. Curtice Consulting. The new CMC models operate over a bandwidth of 0.04 – 6.0 GHz, and offer accurate simulation of amplifier intermodulation and harmonic distortion. The models offer a scalability factor of 30:1. At present, there are about 25 models with more in the works. According to vice president John Quinn, the CMC models offer significantly improved accuracy in predicting device performance over a wide range of conditions including class A/B for high linearity applications as well as deeper back-off (class B and E) for more novel circuit approaches.

To further solidify its position in the wireless infrastructure market, Freescale Semiconductor added 2 GHz sixth-generation members in plastic packages to its line of LDMOS power transistors for 2.5G and 3G applications. The plastic family initially includes MRF6S19060N/NB, MRF6S19100N/NB, MRF6S21060N/NB, MRF6S21100N/NB. By comparison to ceramic equivalent devices, the plastic versions offer 20 percent lower cost and thermal resistance with higher power and efficiency at the same linearity levels. Plus, the 2 GHz plastic RF power transistors are qualified at 200°C maximum die temperature.

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