Found in a 1964 Electronic Design, this circuit makes use of FETs of the time. These transistors can be replaced by modern general-purpose types. The input resistance is 30 M.
This circuit appears in several configurations in this site. This is from American documentation from...
The instrument of this field strength meter, from a 1970s publication, can be a 200 uA...
August 2017 - Mouser Electronics is making available the Gen III generation of Vishay P Channel...