Found in an English publication from the 1980s, this circuit can be built with equivalent transistors such as the BC549. The signal must be applied to an external amplifier.
This circuit was obtained in an American documentation translated in the 80's. The circuit can be...
This circuit is from a 1998 Electronics Now and can be easily assembled since it uses a common...
This circuit was suggested by National Semiconductor in its Linear Application Handbook. The...