Suggested by Sprague in the 90's documentation, this circuit applies to AC motors. The documentation does not indicate the maximum engine power that can be controlled.
This circuit is from an English book from the 1980s. Transistors can be general-purpose types of...
This circuit from the 80's can be easily implemented but needs some changes to avoid problems with...
The presented circuit provides an output voltage proportional to the input current, according to...