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ABOUT FREESCALE AFT09S282NR3 OPERATING CONDITION

Question asked by TONY CAI on Oct 9, 2019
Latest reply on Oct 18, 2019 by TONY CAI

To whom may concern,
I use AFT09S282N Transistor from NXP (formerly from Freescale) to achieve 53.5dBm (equals to 225Watts) RF peak power in Pulse mode in my transmitter module with the following pulse specifications:
Pulse Width: 250 μsec
Pulse Repetition Interval: 1250 μsec
Using the above parameters the average RF Output power is 45Watts which has a great back off from the transistor maximum average power which is 80Watts as reported at the transistor datasheet Rev. 0, 10/2012.
I have mounted the transistor on a brass carrier (or copper carrier) as a flange and the module is well cooled so the final flange temperature of the transistor is about 70° Celsius at 225W RF peak output power.
The operating working frequency is about 850MHz and the matching networks are realized on a 0.02” Rogers RO4003 PCB.
Gain, Output power and efficiency seems to be normal due to ADS simulations (using the large signal model published by NXP) and my measurements on the module.
The problem is that after continuous operation (several days for example) of my module, the transistors begin to fail on several modules. The transistor gate becomes short circuited.
My questions:
1. Is this transistor suitable for my pulse condition (250μsec/1250μsec) with 225W RF peak power and 45W RF average power?
2. Is 70° Celsius suitable for long term operation of this transistor?
Any additional guidance and recommendations will be appreciated.
Sincerely yours.

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