This circuit is from a 1980's documentation for telecommunications. The circuit is used in SSB and the diodes must be suitable types for the application. The audio input is low impedance.
We found this circuit in an article in Electronics Now magazine from March 1996. The frequency is limited...
This circuit is designed to measure very weak currents, in the nanoampères range, using the 1 V...
This circuit is from a 1967 US publication. The configuration can serve as a basis for designs...