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.
We found the configuration below, with unit gain, in the National Semiconductor Linear...
This circuit is from an Electronic Design from the 90's. The main integrated circuit is uncommon...
This circuit appears on this site from different sources. This is from documentation from the...