I'm trying to design a differential ADC circuit using the TI ADC10065 chip. It's a 10-bit, 65 MSPS ADC. In the datasheet they provide a sample circuit with a transformer in it. There's also a circuit generated by TI's ADC topology tool. It uses a differential op-amp.
Now I have a few questions:
I think I can tell what resistor/capacitor values to use for R5=R6=18 ohms
, C1=C2=25 pF
. Is this correct?
Is there a reason I should be using one circuit over the other? Why? I remember reading a document somewhere recommending the differential op-amp method for higher frequency ADC's (it came from another semiconductor manufacturer, don't remember which one).
How do I choose the value of RT
(termination resistor)? Is it even necessary?
For R1/R2
and R3/R4
are there any design considerations I need to take into account such as matching impedance, or am I free to choose any R1=R3
and R2=R4
which meets the desired gain I want?
Should I buffer the input to the transformer/differential op-amp with voltage follower op-amps?