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AD8368 - Input gain control

Question asked by veera on Sep 15, 2012
Latest reply on Sep 18, 2012 by jdobler

Hi,

We are planning to use AD8368 in VGA mode and to have a resistive voltage divider module to control the gain voltage. The gain control will be applied only during the initial calibration process, and after we get the required output power at the end of our transmit module, we will have a fixed resistive voltage divider circuit for gain control rather than potentiometer. Our doubt is what should be the ideal resistor values for divider circuit? Please find the attached diagram detailing our approach.

 

We will be using same power source(ADP3XXX regulators) which we are feeding to the AD8368 to the voltage divider module as well. Does the Gain control pin has any input resistance/capacitance value which may affect the voltage divider circuit? I think the gain control pin to have high input resistance in Mega ohm range, so that if we construct our voltage divider in Kilo ohm range, that should be fine. Am I correct here ?

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