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.
This circuit was found in a 1989 publication. The operational amplifier supports equivalents. The...
This humidity sensor indicates the different levels of conduction of the sensors through an LED...
Found in documentation from the 70s, this circuit uses components from that time. Some of these...