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.
Despite being from a 1970 General Electric documentation this circuit can be used as a shield if...
This is another quick adder that we found in an Electronic Design from the 80s. It also applies to...
This circuit was found in a 1969 Mullard documentation. Used transistors can be replaced with...