This circuit appeared in Radio Elecronics magazine in 1968. The operating circuit is a general-purpose type at the time and the power supply must be symmetrical.
We found this circuit in a 1976 documentation. The FET can be BF245 or MPF102 and the power supply...
This circuit was obtained in a transistors manufacturer's manual from the 90s. The circuit uses an...
The instrument of this field strength meter, from a 1970s publication, can be a 200 uA...