Philips Semiconductors, the largest European semiconductor manufacturer, has introduced a family of LDMOS RF power MOSFETs for use in cellular basestation and UHF broadcast transmitters. In addition to the advantages of higher gain, simpler biasing and lower intermodulation distortion offered by LDMOS FETs (compared to silicon bipolar transistors), these new devices from Philips Semiconductors feature considerably higher bandwidths. As a result, a single Philips Semiconductors device can be used to cover the entire 840 MHz to 960 MHz or 1.8 GHz to 2.0 GHz cellular radio bands. Similar transistors from Philips Semiconductors will soon be available to cover the 2.0 GHz to 2.4 GHz band used for cellular radio in Asia-Pacific.

"The introduction of our LDMOS RF power transistor range demonstrates Philips Semiconductors' commitment to remaining a one-stop-shop for all the semiconductor devices required in cellular radio basestations and broadcast transmitters," explained product marketing manager Volker van Hoorn. "Our position as a universal supplier of components for this market is further enhanced by our circulator and isolator products, and by the extensive range of RF components offered by our passive components division," he added.

Philips Semiconductors' initial range of LDMOS FETs includes four BLF10xx-series devices for use up to 1 GHz, four BLF20xx-series devices for use up to and beyond 2 GHz, and a high power device (the BLF861) for use in 470 MHz to 860 MHz UHF broadcast transmitters. This gives Philips Semiconductors one of the widest ranges of high-power LDMOS RF power transistors on the market. BLF10xx devices provide power gains in excess of 13 dB and are capable of delivering load powers of between 10 W and 90 W. The BLF20xx devices achieve better than 10 dB gain and deliver load powers between 10 W and 140 W. The BLF861 is a 120 W device with a gain of over 14 dB.

Wherever necessary, these new LDMOS FETs feature internal input matching, while the higher power devices also feature integral output matching. They also feature a patented isolation shield that significantly reduces feedback capacitance, plus exceptionally low source inductance and series gate resistance, all of which contribute to high gain and bandwidth. As a result, these transistors are extremely easy to use in power amplifiers for several classes of operation. In particular, their excellent linearity allows designers to take advantage of the efficiency advantages of Class-AB operation, where the transistors' very low level of intermodulation distortion at low power levels also enhances the performance of multi-carrier transmitters.

Philips Semiconductors LDMOS power MOSFETs are also rugged. In addition to the freedom from thermal runaway inherent in the LDMOS structure, they also feature gold metallization and silicon nitride passivation to enhance long-term reliability. Their grounded substrate construction, which eliminates the need for an insulator between the transistor die and the mounting flange, guarantees a low junction-to-case thermal resistance that allows them to run cooler. The absence of beryllium oxide (toxic) in the package also makes them environmentally friendly.

Sometimes the surprises come totally out of left field. This press release should, of course, have Motorola's name at the top of it. It is always reassuring that a manufacturer not only agrees with you that LDMOS technology is great but then also goes for it themselves! This is an impressive family and Philips interest in achieving these numbers at these frequencies in undoubtedly fuelled not just by the extremely profitable base station market but also by the very healthy profits that can come from the broadcast industry, an area they have been playing in various guises for decades. My own feeling is that these power levels are close to maxing out for the technology -- maybe another 3 dB more -- and then we will have to go full bore on SiC.

Philips have great experience at RF with some extremely competent designers so when they give numbers I believe them. These will be extremely profitable product lines. Some of the family is available now and volume production is scheduled in the last quarter of 1998.