This lockable two-position servo control system was found in documentation from the 1990s. The error amplifier can be an operational amplifier and the sensors are phototransistors.
Found in an old Elektor, this circuit uses two 7-segment displays to indicate the volume of an...
This resistance meter has a linear scale, converting resistances to voltage. The operational...
I got this circuit from an English magazine from 1977. It can still be easily assembled, as the...