Hello...
I working in an application where the objective is to amplify a signal which is not know the exact frequency, but is estimated between 100kHz and 20MHz. Similarly amplitude is not known, this is considered less 100nV and one might expect so small as undetectable (pV-fV). To know the presence of said signal is intended to design an amplifier with a variable gain range of 4V/V - 10GV / V formed with multiple stages based on the LMH6629 which was chosen for its bandwidth (900MHz) and the noise level 0.69nV / √ Hz which is the lowest I could find. The input impedance is less than 50 Ohm.
the output of this amplifier is the entrance to the filtering system with an amplifier LOCK IN.
I appreciate suggestions on how to maintain a level of noise and variable gain acaptable the LMH6629.