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 frequency modulated light transmitter is from a 1990s documentation. The circuit may use...
This circuit was found in 80's documentation from Analog Devices. The formulas for calculating the components...
This circuit was found in Siliconix documentation from the 1980s. Common comparators or...