This dual balanced modulator configuration was obtained in a 1980s telecommunications documentation. The circuit makes use of transformers and the diodes are commonly used.
Delivering Over 4X More Battery Life and Faster Time to Market, Platform Comes Complete with...
I found this circuit on a December 1976 Radio Elettronica. The Italian magazine no longer exists, but...
This circuit, indicated by Texas Instruments, uses a high voltage regulator and a Darlington also...