This circuit was found in a 1967 Raytheon manual. The transistors are from the time. Equivalent modern transistors can be tried out.
The input resistance of this circuit is 60k and the pass band from 20 to 20kHz. The circuit is...
This PWM control circuit was found in an old documentation, but appears elsewhere on this site...
Maxim MAX25612 High Voltage LED Controller In stock from Mouser Electronics, this high voltage...