Ericsson Components has launched a line-up of two RF power transistors aimed specifically at the European DAB (Digital Audio Broadcast) transmitter market. With a peak output power of 135W, both transistors use GOLDMOS technology, offering excellent linearity and thermal stability.

Working in the 1.4 to 1.6GHz frequency band, the 28V line-up comprises of the 30W PTF10021 and the powerful PTF10125, giving a minimum output of 135W. Total gain of the line-up is an impressive 22dB, exhibiting a high peak to average power capability.

Because both devices are LDMOS (Laterally Diffused Metal Oxide Semiconductor), RF performance in the line-up is significantly improved. Gain is typically around 3dB higher for each device than its bipolar equivalent. Class AB linearity is also better - for example with a typical gain of 13dB in the 1.4 to 1.6GHz range, the PTF10021 exhibits a flat response of just ý0.1dB.

Power dynamic linearity - which is crucial in DAB applications - is superior for LDMOS technology. With a bipolar line-up, linearity is power dependant, so as power output decreases, so does linearity. However in Ericssonýs all-LDMOS line-up, linearity is assured at reduced levels of output power, thus simplifying amplifier design and reducing costs.

Another advantage of using LDMOS is thermal stability, as load mismatch and overdrive tolerances are superior to bipolar devices. LDMOS technology is unique in that the drain current decreases with an increase in temperature. Because of this, the risk of thermal runaway is greatly reduced, enhancing reliability.
Designed to work from a standard 28V supply, drain-source breakdown voltage for the line-up is 65V. Ion implantation, nitride surface passivation and gold metallization ensure excellent reliability and ruggedness for the two devices. Both transistors offer 100% lot traceability to allow complete quality assurance.

Both Band III (174 to 240 MHz) and L-Band (1452 to 1492 MHz) Eureka 147 digital audio broadcasting are very real in Europe -- and many other parts of the world. While the United States has gone through multiple trials and tribulations over DAB, mostly band-arguments and the usual lack of direction from the FCC, the BBC offers DAB coverage in the UK to 30 million people with 60% of the country covered; they simulcast the five national program channels and they offer additional sports and parliamentary coverage. Belgium covers 70% of its population, Israel 70%, Portugal 50%, and so on. Even our neighbors in Canada have 30% coverage, Australia is in trials. Korea has adopted the 147 standard and even Japan is considering it -- though they would have much preferred to go American.