AnsweredAssumed Answered

ADA4937 Output series Resistor

Question asked by YYHH on Nov 11, 2011

I'll drive the 14-bit AD9255 ADC, sampling a 35MHz signal at 88MHz, with a ADA4937.

I read a couple of application notes, like AN742.

So, "the key is to make the input look as "real" as possible to achieve a good impedance match".

ADA4937.png

Output (R,C) acts like a LP Filter, and L cancels the Reactance saw by the driver.

The question is : How do I choose the best value for the series output resistors? 200 Ohms or 1k are the clasical values given in the ADA4937 datasheet. Distortion seems a bit better with a 1k output series resistor, but there is for example a lot of application notes using a 33ohms output resistor.

 

 

 

Outcomes