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AD8310 Settling Time

Question asked by zach.horn on Jun 11, 2014
Latest reply on Jun 23, 2014 by jdobler

Hello. I am using the AD8310 to measure signals from 10kHz to 1MHz. The signals I am measuring are CML (about 600mV peak-to-peak). When the stimulus is applied to the AD8310 the output overshoots and takes an extremely long time to settle. My schematic and the output response are attached.


In the schematic, the 2.74kohm resistors form a voltage divider with the 105ohm resistor to reduce the signal level to the AD8310's linear range. The 2.2uF and 18pF caps set the input frequency response. The 18kohm resistor doubles the gain. The 0.047uF cap provides some output filtering. The 0.1uF cap at pin OFLT reduces the high-pass corner of the amplifier's offset correction loop to about 600Hz.

 

If I removed the cap at OFLT, there is no longer any overshoot.

 

It seems impossible that the offset correction could have such a long settling time. We are stumped. Any suggestions?

 

Thanks.

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