Other versions exist on this site from various publications. This one is from the Radio Electronics Experimenter from 1990. The bargraph circuit uses the UAA170.
This is the normal configuration for the TDA2003 integrated circuit, an amplifier that can provide 10...
Found in an English publication from 1977, this circuit uses only 1 LED. Unlit means heads and lit...
In the figure we have the transmitter and the receiver for an optical audio link via infrared. The...