This circuit was obtained from an Electronics Design of 1964. The circuit makes use of tunnel diodes that are uncommon today. The circuit works with very weak signals.
We found this circuit in a 1968 Electronics World. The transistors are from the era and...
There are several manufacturers of the integrated circuit used and it also admits equivalents. The circuit...
This circuit is from 1971 American documentation. Transistors are still common except for 2N2060...