Found in American documentation from the 1980s, this circuit has a diode feedback. At the exit we have an indicator LED. The LM3900 is a transconductance operational amplifier.
LEDs are diodes and can be tested with a simple configuration that allows the display of its...
We found this circuit in a European schematic from the 90s. The used integrated circuit can still...
This circuit was found in the June 1990 issue of Radio Electronics magazine. Integrated circuits must...