We found this circuit in a Poptronics from the 90's. Equivalent operational amplifiers can be used. The circuit must be supplied by a symmetrical source.
This circuit was found in the January 1995 Electronics Now magazine. Its configuration is valid for...
This circuit with transistors in parallel was found in a Radio Electronics of August 1952....
We find this simple circuit in an English publication called Electronic Circuit Design no. 3 of...