It can be LM108 and LM112 (internally compensated) and there is absolutely no trick there. It's 1nA enter bias which is rather stable with temperature as in many bipolar opamps because β essentially enhances with temperature. Later on iterations like LT1008/LT1012 or OP97 pushed it down to The technological storage https://andreiy222ysn6.vblogetin.com/profile