Using a 4046 PLL this circuit recognizes a 1.6 to 1.8 kHz tone by driving an output LED. The circuit is from a Radio Electronics from December 1989.
This two-transistor amplifier has good gain but delivers a fraction of a watt of power. The...
This circuit was found in the 1969 RCA thyristor manual. The circuit has a limiter (clipping) with two 12...
This small amplifier, with output less than 1 W, was found in a 1960 transistor manual from...