Based on Texas Instruments documentation, this circuit serves for sensor interfacing. The circuit is based on the LF411, but other operational ones can be used.
Using components from the era, this 90's EDN circuit is used in analog to digital conversion...
Found in an American publication from the 90s, this circuit allows the supply of 3, 6 and 9 V...
We found this circuit in an old Popular Electronics. The circuit is experimental, driving an LED...