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Driving AD80066

Question asked by pixelPhile on Jul 11, 2017
Latest reply on Oct 11, 2017 by JinoL

I'm using AD80066 to digitize four channels at 4MHz each (so ADCCLK is running at 16MHz).  I'm finding that the buffer amplifier I'm using to drive the ADC is oscillating.  I've tried AD8061, ADA4897-1 and AD8065; they all seem to oscillate at around 100MHz.

The circuit has a 100R resistor between the sensor and the +ve input of the amp.  The amp is configured as a unity-gain buffer.  There's a 51R resistor in series with the output (though about 3 inches from it), then the ADC.
I've looked at various material describing the techniques that are generally employed in PCB layout to prevent stray capacitance (and consequent oscillation).  Unfortunately, one of our constraints is that we don't want significant areas of the board to have both planes missing because of stray light leakage.  And we already have a PCB layout... 

Can you suggest alternative amplifiers that are suitable for driving the ADC and that will be less susceptible to oscillation, or ways to stop the oscillation (preferably without significant changes to the PCB).

Thanks!

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