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high-performance ADC driver; is VGA an option?

Question asked by bob on Aug 9, 2011
Latest reply on Aug 9, 2011 by stevereine
I need a driver for a high-performance high-speed ADC.  The input BW requirement is DC to 175MHz;
the magnitude could be as low as ~100mV, but could be higher as well.  Low noise and low distortion
are very important.  My ADC is a single-rail 5V analog input, 2.2Vp-p VCM=3.1V (400Msps 14-bit).  I
started looking at VGAs to accommodate the potentially wide range of input signal amplitude.


1. The AD8370 datasheet says "LF to 750MHz".  I want to dc-couple the inputs; but there is no
common-mode input range given. Does this mean the part must be ac-coupled, and I must rule out
the AD8370? Is "LF" quantifiable? 


2. If the AD8370 is not an option, I would then look for a std fixed-gain diff amp; any suggestions
would be appreciated.  I need gain around 12dB, input as above (+/- 100mV input), very flat gain
through 175MHz, > 5V supply, low noise, low distortion. 

Thanks in advance.



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