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AD8318 not controlling PA output sensiblly

Question asked by neilsparling on Dec 9, 2016
Latest reply on Dec 10, 2016 by neilsparling

I'm using the AD8318 in controller mode as part of a feedback loop.... controlling the output power of a PA by adjusting the input power dependent on the coupled output power.... but I'm getting unwanted variation. Putting it in log mode I can see a direct output change when I get power out of the amplifier even when manually controlling the input RF and disconnecting the feedback path. I've isolated nearly all of the interfaces and only get a stable output i.e an uninfluenced one when the chip is disabled or I break all of the grounds (the output floats to  5V).

 

Any suggestions ?.

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