Using the 741 this basic circuit was found in the November 1973 Radio Electronics magazine. The power supply must be symmetrical. The components can be recalculated for other frequencies.
This 1000: 1 voltage-controlled filter circuit was found in an Electronics Today International in a 1980s...
In the figure we show how to supply a DC motor from 6 to 12 V with alternating current. The diodes...
Found in a Radio Electronics we have in the figure a circuit to disconnect an SCR with direct...