This circuit was found in a 1967 EEE. The components are from that time, but the circuit can be implemented with modern equivalent components.
This circuit was found in an Electronic Design from the 90's. The maximum output current is 1.25...
This circuit uses a quadruple operational amplifier of the time. The circuit is from the 70s but...
In this Radio Electronics from May 1958 we have the now common use of the varicap in a frequency...