This circuit was found in a 1966 EEE. The circuit uses transistors from the time but can be made with modern equivalents. The operating frequency ranges from 0.1 to 1 kHz.
This circuit is from a Radio Electronics magazine from August 1960. It is a commercial circuit for marine...
We found this filter in documentation from the 1980s. The operational amplifier used is uncommon...
In this circuit, a light-sensitive SCR or Light Activated SCR determines the operation of an...