Using an LDR as a sensor, this circuit is from the Radio Electronics magazine of December 1984. The operational amplifier is the 741 and the source must be symmetrical.
This circuit is from a 1969 Electronics World. The transistors may be modern general-purpose...
This unusual unijunction transistor SCR firing circuit was found in a General Electric...
This “brainwave” amplifier was published in Radio Electronics magazine in August 1964. The...