We found this receiver circuit for modulated light in a 90s Popular Electronics. Equivalent audio amplifiers can be used. Transistors are commonly used.
This circuit consists of two stages that each shift 180 degrees the signal. The circuit was...
This simple battery tester uses two transistors to drive LEDs of different colors, indicating the...
Found in 90s documentation from Analog Devices, this circuit employs operational amplifiers of the time....