This optical coupler for short distances is powered by 12 V which is the voltage of the lamp and the relay. The circuit can also use emitting LEDs and the phototransistor can be of any type.
This is the basic configuration of an operational amplifier sample & hold circuit. The FET and...
This transmitter emits signals in the FM range, reaching a few meters away. The modulation...
This low distortion circuit was shown in the July 1983 issue of Radio Electronics magazine. The...