Missing half the spec.
Frequency range? Noise performance? What 1/f corner? Supply voltage? Current consumption?
50 ohm output resistor or capable of driving a 50 ohm load, these are very different objectives....
Something jfet input feels right (High Z input), but it very much depends on the other parameters, this could be a single opamp maybe with an additional current booster, or it could be several pages of clever circuitry it depends.
73 Dan.