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ADL5535 1PdB - 1dB Compression Point Unterstanding

Hi Folks,

please could you help me to explain the fact, that the ADL5535 has a higher 1dB compression point than the power supply allows?


Example:

1dB P1 = 18.6dB as lowest in statistic, according to Fig.11. of the datasheet.

 

18.6dB is 72.44mW into a 50 Ohm load.

U = SQRT (P*R) = SQRT (72.44mW * 50) = 1.9Vrms

Upeak = 1.9Vrms * sqrt(2) = 2.69V


To run Upeak-peak the Voltage swing is: 2 * 2.69V = 5.38V.

This should be the voltage on the 50Ohm termination.

If we consider the internal driver has a 50Ohm series termination, the driving voltage must have 10.77V. Considering no extra headrom for the transistors to drive the load.


How can the outputpowerlevel of at least 18.6dB be explained?

Is the datasheet correct?


Thanks.


 

Parents
  • This is just a guess, but if the P1dB is specified for a conjugate match to the device output and the real part of the output impedance is less than 50 ohms, then the power output would be correspondingly higher. Looking at the values for S22 provided in the datasheet, it looks like that could be the case. If thomasww is taking his measurements in a 50 ohm system and not matching the output, this might also explain his results.

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  • This is just a guess, but if the P1dB is specified for a conjugate match to the device output and the real part of the output impedance is less than 50 ohms, then the power output would be correspondingly higher. Looking at the values for S22 provided in the datasheet, it looks like that could be the case. If thomasww is taking his measurements in a 50 ohm system and not matching the output, this might also explain his results.

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