This circuit was obtained in a 1980s publication, but it can be easily assembled today, as all components are common. The transformer is 12 + 12 V with at least 1 A and the diodes 1N4002.
This circuit is from an English magazine of 1977. The circuit is still current, just using BC547...
This symmetrical configuration uses two operational amplifiers to obtain the rectification of a...
We found this circuit in a Mullard manual from 1960. The transistor is a phototransistor of the...