The circuit shown in the figure can be designed with more modern operational amplifiers, as it is from 1994 documentation by National Semiconductor. The power supply must be symmetrical.
This transistor source was found in a 1990 documentation. 2N3055 transistors must be equipped with...
This tube circuit is from an 80's documentation. The filter is of the selective type and the...
This general-purpose two-transistor circuit was found in the November 1993 issue of Electronics Now. The...