It is LM108 and LM112 (internally compensated) and there is de facto no trick there. It's 1nA enter bias which is rather secure with temperature as in many bipolar opamps because β truly increases with temperature. Later iterations like LT1008/LT1012 or OP97 pushed it right down to An optical amplifier https://pin-diode-switch58023.blogpixi.com/34444348/considerations-to-know-about-low-noise-amplifier