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AD8367 VGA with Fast Gain Sweep

Question asked by james@iknowsystems.com on Jun 28, 2012
Latest reply on Jul 10, 2012 by james@iknowsystems.com

Hi,

 

I am using the AD8367 as a VGA and I want to sweep the gain from min to max in a short period (400nS).

 

With no input (input grounded through 200 ohm in series with 330pF) I am getting an offset ripple of about 600mV during the gain change.  I have attached a picture of the waveform.  Channel 1 is the Gain signal and 2 is the output.  I have HPFL open, DECL cap of 10nF, Mode grounded, and DETO grounded.  The output is terminated with 200 ohms in series with 330pF.

 

Is this output ripple normal?  What causes the output ripple?  What can I do to reduce the output ripple?

 

Thanks,

James Donald

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