AnsweredAssumed Answered

AD8347 BB input biasing

Question asked by Roman.Sh on Jan 29, 2013
Latest reply on Jan 29, 2013 by bsam

Hi,

According to application note the Base Band inputs IAIN, QAIN and detectors VDT1/VDT2 should be biased with Vref (1V). For my reasons I need to bias these pins from other source which is also ~1V, however in this case I have a failure in the AGC loop it became constantly at minimum gain (VAGC = 3V). What could be the cause of this strange behavior. One reason I can thought about, is that the detectors are working with internal Vref (internal band gap reference), and if I apply voltage that is even 50mV larger than Vref it clips the AGC to minimum gain.

 

Please advice, what could be done to resolve this problem.

 

Thanks,

Roman

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