Found in a 1967 American electronics magazine, this circuit has an input impedance of 2000 ohms. The circuit can be built with modern equivalent transistors.
We found this circuit in an old documentation from the 70s. The sensor is an LDR that must be...
This circuit with junction field effect transistors was found in documentation from the 1980s. The...
Common general purpose silicon diodes when direct biased provide a voltage fall of about 0.6 to...