We found this circuit in a 1982 documentation. It uses a CA3140 or equivalent operational amplifier and does not require a symmetrical source. The output is 1 Vpp wide.
Found in American documentation from 1968 this circuit is based on discrete components in addition...
This simple circuit indicates, through an LED, when the water level of a filter (or other kind of...
This circuit appears in similar versions elsewhere on this site. The transformer is 110 V or 220 V...