Quote:
Originally Posted by BradP01
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Hi,
Can someone offer some insight please relating to absolute maximum ratings of RF devices? I outline an RF FET case study below:
Absolute maximum rating from datasheet
Vgsmax=-10 to +3V
Relevant Device RF Data @ operational Frequency
Zin=+17.8-j16.
Relevant Operational Details
RF power in=29dBm (794mW)
Quiescent Gate Voltage=-1V (DC bias)
Calculations
I did a fundamental Ohms law type calculation to determine what the RF voltage swing would be on the device input (Gate)
Vpp=2*sqrt(2*P*Zin), Vpp=12.3V so that the RF swing is between -7.2 and +5.2V. The analysis suggests that at the top of the RF swing, the device Vgsmax is exceeded, and this can therefore be seen as a potential failure scenario.
I have posed this question to colleagues, some of whom claim that the Absolute Max rating described is purely a DC parameter, and that that it did not apply to RF. Same colleagues however, could never provide theoretical validation of this assertion.
Can someone please validate the logic here or otherwise explain why the thinking is flawed and offer an alternative idea to relate absolute DC limits and operational RF extremes.
Thanks,
BK Parker
Can someone offer some insight please relating to absolute maximum ratings of RF devices? I outline an RF FET case study below:
Absolute maximum rating from datasheet
Vgsmax=-10 to +3V
Relevant Device RF Data @ operational Frequency
Zin=+17.8-j16.
Relevant Operational Details
RF power in=29dBm (794mW)
Quiescent Gate Voltage=-1V (DC bias)
Calculations
I did a fundamental Ohms law type calculation to determine what the RF voltage swing would be on the device input (Gate)
Vpp=2*sqrt(2*P*Zin), Vpp=12.3V so that the RF swing is between -7.2 and +5.2V. The analysis suggests that at the top of the RF swing, the device Vgsmax is exceeded, and this can therefore be seen as a potential failure scenario.
I have posed this question to colleagues, some of whom claim that the Absolute Max rating described is purely a DC parameter, and that that it did not apply to RF. Same colleagues however, could never provide theoretical validation of this assertion.
Can someone please validate the logic here or otherwise explain why the thinking is flawed and offer an alternative idea to relate absolute DC limits and operational RF extremes.
Thanks,
BK Parker