AD8332_overloading

Document created by analog-archivist Employee on Feb 23, 2016
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Hope you are well. One AD8332 question need your help. Attached is the
schematic.

Below is several waves. The Gain of AD8332 is 40dB.
Wave C is the AD8332's LNA's Input, it's a 1MHz negative pulse, the amplitude
is -750mV, and Wave B is the AD8332's Output. The customer is not sure why the
AD8332's output will distort. I think -750mV amplitude have exceeded AD8332's
input range which is +-275mV.
Hope you can give some advices.

 

Thanks for feeding this question back to us.  Who is the customer and do you
know what application they are using this for?  When the part is driven with a
low frequency like 1 MHz, there is a significant amount of charge that gets
stored in the device creating the slow recovery transient that the customer is
observing.  This is why the AD8332 does not recover from slow frequency over
drive states as well as it recovers from fast frequency over drive states. 

Jim actually wrote up a section in the data sheet that outlines an application
circuit that can help deal with overdrive.   It involves clamping the input
voltage with diodes to make sure the AD8332 does not get over driven.  It is
outlined in detail on page 32 of the datasheet
http://www.analog.com/static/imported-files/data_sheets/AD8331_8332_8334.pdf
By clamping the input voltage as outlined in the data sheet, the user can
prevent the long over drive recovery transients.  Please let me know if you
need any more information to help out.

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