@niconiconi I would have mentioned the ADA4530-1 opamp, but the bandwidth requirement won't be met, as it's in teraohm ranges
Though 3 millivolt isn't that bad perse, as there are tons of instrumentation opamps that will have picoamps of input bias current. Obviously a noninverting amplifier would be the best bet, but I would assume most MOSFET based precision opamps would do the trick?
Don't know enough about the application to give a better answer, but I deal with this kind of stuff at work on a daily basis
@bit0fun@qoto.org The intended application is amplifying a wideband Rogowski coil's response to kiloamp-level impulse current for surge waveform measurement, so I can have an alternative to shunt resistors.
I've just checked the literature, and found Rogowski coils generally requires a parallel damping resistor, so the input impedance needs not to be high-Z, and can actually be relaxed to 50-100 Ω. That certainly makes everything easier, as standard RF design practices are now possible.