RF power transistor for 870 MHz base station and ISM applications
The NXP AFT09MS031GNR1 is an LDMOS RF power transistor rated for 40 V drain voltage, delivering 31 W output power at 870 MHz with a gain of 17.2 dB. It comes in a TO-270BA surface-mount package with a gull-wing lead form (TO-270-2 GULL). This part is designed for 870 MHz band applications such as cellular base station final stages, ISM-band RF generators, and industrial heating or plasma drivers where linearity and efficiency at moderate power levels are required.
17.2 dB gain and 31 W output — what these mean for the RF stage
At 870 MHz and a test bias of 13.6 V with 500 mA quiescent current, the 17.2 dB gain figure means a drive level of roughly 0.6 W at the input yields the full 31 W output. This gain is typical for a single-stage LDMOS device at this frequency and power class, so a driver stage with moderate output (1–2 W) can directly feed this transistor without an intermediate gain block. The 31 W output is the saturated or linear power capability depending on the class of operation — for class AB linear service (common in cellular PA stages), the usable linear power will be a few dB below that figure, so budget the back-off when sizing the stage.
Package and mounting — TO-270BA surface-mount gull-wing
The TO-270BA package (TO-270-2 GULL) is a two-lead surface-mount package with a gull-wing lead form and an exposed metal tab for thermal and electrical connection to the drain. The mounting type is surface mount, so it reflows onto a standard PCB footprint. Without that thermal path, junction temperature will exceed the safe limit at 31 W continuous output.