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ADL5380 ADJ resistor value 3-4 GHz

Question asked by AMB on May 10, 2013
Latest reply on May 15, 2013 by AMB

In the ADL5380 (Quadrature demodulator 400MHz - 6 GHz) datasheet, the recommendation in the 3-4 GHz frequency range is to set the ADJ resistor to 200 ohms to Vs to give Vadj ~ 4.8V.  See e.g. table 3, header on page 11 and table 4.

 

However, figure 26 shows that setting Vadj ~ 2.4V (as for 5-6 GHz) gives higher IIP3 and lower noise figure compared with Vadj @ 4.8V.  The only disadvantage seems to be degraded IIP3 at lower temperatures.

 

So why is it recommended to set Vadj ~ 4.8V for the 3-4 GHz frequency range?  Why not 2.4V?

 

Many thanks for your help!

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