Determining Maximum RF Output Power Rating
By Richard Frey, P.E.
Senior Applications Engineer
Advanced Power Technology
There is a fairly wide variation between manufacturers in the method used to specify a device's RF output power. There are many factors to be considered and the foregoing is provided as a guide to a successful design and explains the cause of those differences.
There are several basic principles involved plus a few intangibles to make it less precise. We define drain (or collector) efficiency as
and then define
We can then define rf output power (Po) in terms of efficiency and power dissipation:
In cases where the RF gain of the device is low and the drive power is a significant portion of the input power, i.e. G < 10 dB, Pin should include the drive power. In this case it is called power-added efficiency, PAE.
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