One your friend beg for model the circuit about variable supply range 0-25V. I tries to search see meet voltage regulators circuits. The this be the circuit that use the transistor 2N3055 numbers are important equipment. Which be the equipment that seek good easy. fine P1 control current output the topmost.And fine P2 control Voltage range 0-25V.
The detail is other invite read in original website http://www.redcircuits.com//Page36.htm