It is really LM108 and LM112 (internally compensated) and there is basically no trick there. It's got 1nA enter bias that's rather secure with temperature as in most bipolar opamps because β actually enhances with temperature. Later iterations like LT1008/LT1012 or OP97 pushed it right down to For an in-depth https://alfredo999xsk5.wikibuysell.com/user