It is my first project with a high speed op amp, so I would like to ask a few questions about using the ADA4817 before starting the prototype, to avoid basic errors.
My project consists of reproducing a differential probe with characteristics similar to Keysight's N2792A tip (10:1, 200 MHz, output ± 2 V, 1 MΩ // 3.5 pF between inputs, differential ± 20 V, common mode ± 60 V).
This design I believe consists of three stages:
1) Input attenuator;
2) Non inverters for buffering;
3) Subtractor, converting the differential inputs into a single output;
To be able to go ahead and make the first prototype are, I wish to know:
1) Can I remain with unit gain on the preamps and on the output subtractor, and perform all necessary attenuation only on the RC input attenuator? I see that ADA4817 its unity gain stable, my -3dB operating frequency its on the range for the signal's amplitude, feedback resistor and crossover frequency checked.
2) Can I have ADA4817 non-inverters with unit gain, using 200R feedback resistors and without the gain resistor Rg (like datasheet states at page 27, just after equation 16)?
3) Considering that the maximum output amplitude happens only when a signal at +20 V and another at -20 V, so the subtractor will perform output 1 - (- 1) = 2 V, can I consider that the circuit operates most of the time with small signal characteristics? In addition, the datasheet states that the Input Common-Mode Voltage Range from −VS to (+ VS - 2.8). My source will be ± 5 V, so I think its ok in that point.
4) Is there a problem with using low values like 350R in the subtractor resistors?
5) The feedback pin FB on the ADA4817 packages it's only a clever way to route feedback signal from the output? It's a good idea to use it for feedback traces?