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.
Found in old documentation, this circuit is the receiver for the previous circuit. Components are...
This high input impedance amplifier stage was found in a 1963 documentation. The transistor...
This circuit was found in the June 1991 issue of Radio Electronics magazine. The circuit uses two...