ADS4222: the interface between differential op and ADC

What does 1K load means in my circuit? 

The ads4222 differential input resistance is 0.75kohm. 

So should set Ro = 0.25kohm and Rload= Not installed ?

Hi Rob,

I would put Rload --> what does it mean? installed or remove?  if install, what resistance value should be installed?

I don't understand how do you achieve 1K ohm based on above comments,  49.9 ohm + 5~15 ohm + 0.75Kohm ?

Hi Shen,

I apologize for the confusion, 1Kohm was just an example.

The resistor value would be dependent on the gain and input configuration you plan to use for your application.

Once we know those, we can use the tables (4&5) in the THS4521 datasheet to determine the resistor values needed for the interface.

Regards,

Rob

Hi Rob,

The table 4&5 is for Rf and Rg. I think it's different from our topic about the output interface with ads4222.

What I want to know the resistor value Ro and Rload setting between THS4521 and ads4222?

by the way, my application is using single end and 1 Gain.

Hi Shen,

thank you for the information, this helps.

Last question before I can recommend a circuit for you.

Do you plan to DC couple between the output of the amplifier and inputs of the ADC?

Or AC couple, ie - use an AC blocking cap to break the VCM differences between the amp and ADC?

Regards,

Rob

Hi Rob,

I plan to use DC. 

Hi Rob,

Thanks for much detail explanation.

So the target is to set Rb//Radc = about 1K ohm, is this understanding right?

One more, what's the purpose of Ra and Rc?

Hi Rob,

Should I reserve capacitor like below? Make sense or not?

My application is 50M sample rate.