AD8302: VPHS output changes with different input signal amplitude

Document created by analog-archivist Employee on Feb 23, 2016Last modified by analog-archivist Employee on Feb 23, 2016
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There is a question about AD8302 as below. I connect the node 1 and node 2 with
VINA and VINB as below. When I changed the amplitude of input signal V1, the
output of VPHS will change too. When V1=120mV, VPHS=1.79V; When V1=10mV,
VPHS=1.26V. Actually, the phase did not change with the amplitude of V1, the
VPHS should not be changed. Would you kindly give some professional suggestions
on this issue? BTW, the output of VMAG is always correct.

 

Please increase the value of the filter caps and the input caps as they are not
suited for such low frequencies.  Page 13 of the AN-691 application note "
Operation of RF Detector Products at Low Frequency" discusses low frequency
operation of the AD8302. The shift is coming through the cap to gnd. Please see
Figure 1 in the attachment.

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