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 old fashioned amplifier can source some watts to a low impedance loudspeaker. The circuit...
This circuit is from a Radio Electronics from September 1969. The integrated circuit used is one...
This CMOS circuit is re-triggerable. It was found in the April 1988 issue of Radio Electronics...