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AD9635 with ADA4927 as driver


We need an ADC setup to sample a single-ended IF signal. We are considering the AD9635 as the ADC with the recommended ADA4927 as driver and to perform the a single-ended to differential conversion.

The IF signal has beat frequencies down to 1 kHz and up to 12 MHz and the plan is to do baseband sampling.

1) Is this a feasible setup?

2) I can't seem to find an example of any of the recommended driver amplifiers (ADA4927 or ADA4938) driving the AD9635. Can you point to an example?

Thanks, Claus

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  • Hi Xavier,

    Thanks for your quick reply.

    I looked at the schematic for the EVAL board as you suggested, and tried to simulate the ADA4930 design in the DiffAmpCalc. The design around the ADA4930 seems to be based on Input Common-Mode Adjustment with Resistors as described in the ADA4930 data sheet page 22. I don't think DiffAmpCalc can simulate that design approach, or am I missing something?

    Anyway, I believe I get the idea of how to configure an ADA49xx.

    There is not much information in Wiki or the design and integration files about how to use the optional active path (the ADA4930) on the EVAL board. I have pieced together the schematic for the network between the ADA4930 and the ADC from EVAL board. I have removed all the DNI components. The schematic in the picture is what remains. 

    Are the components in the blue box necessary? The ADA4930 already provides a common-mode voltage and I would remove R412 and R413. What is the purpose of R433/R434? Maybe they are just part of the RLC place holders for a potential filter, but they are not marked DNI as the rest of the place holders?



  • Hi Claus,

    I apologize for the late reply.

    I made a mistake for the comment I made for this and yes, you are right. To correct, you do not need the blue box when employing VCM at ADA4930.