Found in an Electronics World of 1968, this circuit is indicated for applications in photography making the control of a camera aperture. The components are from the time.
Using a CA3130 operational amplifier, this circuit was found in an English publication from 1977....
The L79xx is the SGS version of the 79xx. The circuit was obtained in the SGS manual of linear...
This sophisticated circuit with two LF411 operational amplifiers appeared in the November 1984...