This filter is from a 1977 publication. The circuit employs three 741 or other operational amplifiers. The supply must be symmetrical and the components with (*) are low tolerance.
This amplifier was published in the July 1961 Radio Electronics magazine. It announced the release of...
This circuit was found in a 1967 Electronics World. SCRs are according the controller load,...
This sophisticated circuit using a liquid crystal display was found in Radio Electronics from the...