Found in a 303 Circuits from the 90's this circuit can use the lowest current range of a common multimeter. The circuit can measure currents as low as 100 pA.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...