This circuit doubles the frequency of a rectangular signal applied to its input. The circuit has a 30 kHz input to obtain 60 kHz signals. We found it in a 1964 Electronic Design.
This circuit was found in documentation from the 70s. We can try current JFET transistors....
This is the power supply circuit for the amplifier in the previous circuit. The source is...
This bridge circuit is designed for 8-ohm speakers delivering a few watts of power. The circuit is from...