This circuit was found in an American publication in 1966. The circuit uses a general-purpose FET that admits an equivalent. The instrument is a 250 uA full-scale microammeter.
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...