THS3217: Changing Resistor Values

Hello Elisha, 

The interstage network is intended to be pretty flexible including the idea of adding image reject filters right there. Often the high speed dacs are specified with a 50ohm at their outputs to ground (for current sourcing DACs) and the a 50ohm trace to 50ohm termination R's at the THS3217 inputs - hence the 25 ohm. If there is any trace length at all, and you want a 100ohm net termination, that wouldthen be 200ohm at the DAC, 200ohm traces, then 200ohm at the inputs. 

All of that is fine, the things that will change  are - 

1. more gain for the input Ios error (the higher Icm*100ohm will get rejected in the D2S stage)

2. Higher noise - that would simulate easily and might not be a big shift given the other terms. 

There is some interesting detail in this reference design

http://www.ti.com/tool/TIDA-00684

Here is the full interstage design used here, That should be MHz not mHz filter

Hi Elisha, 

Adding on to Michael's response. The THS3217 generally will not have a problem with whatever value resistors you want to use on the inputs. The most important thing is to make sure you match the impedances properly to the DAC output so that it is loaded properly and that you don't have any reflection issues if you are using long traces. 

Regards,