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450W RF power transistor takes on UHF broadcast TV

Designers at Freescale are not fooling around. For the past two years they have been releasing product in their 50 V laterally diffused MOS (LDMOS) process. Now they are delivering an RF power transistor that targets the entire UHF band for broadcast TV (both analog and digital, of course), and the company reports that this new MRF6VP3450H device delivers 50% more power than its closest competitor.

Percentages are nice, but here are numbers for you: 90 W average RF output power at 860 MHz for DVB-T and 450 W peak-envelope- power (two-tone test) with 21.5 dB minimum gain, 23 dB typical gain.

This level of gain and power allows for tighter designs, such as providing 320 W average output power with only two gain stages and five devices. In addition, the designers at Freescale had their eyes on reducing system-level power consumption with this device, aiming to help reduce operating costs for broadcasters. To achieve this, Freescale's Product Manager Pierre Piel reports they had to “pay careful attention to the thermal design of device and maintain low junction temperatures, which makes the part act more efficiently.” The MRF6VP3450H is specified with 28% typical drain efficiency for a DVB-T 64 QAM OFDM signal and 45% efficiency in a two-tone test.

Finally, the design team wanted to make this part rugged. When operating at 50 V and 90 W average DVB-T OFDM, it can survive all phase angles of a 10:1 VSWR. Similarly, it will survive the same mismatch operating at 450 W peak pulsed power (10 μs pulse, 2.5 percent duty cycle). The device also incorporates protection against electrostatic discharge (ESD).

The timing of this product release is very good, and for those of you designing in this space, it is definitely worth a closer look. The MRF6VP3450H is sampling now, and application demo boards are available. Freescale expects to be in production for MRF6VP3450H in Q3 2008. In the meantime, you can check out the data sheet at: www.freescale.com/rfbroadcast.

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