International project (1251?78 and 1252?78) in which the Technical University of Sofia (S.Valtchev, N.Stefanov) has sucessfully acomplished the task of constructing and implementing in production a high precision (0.01% regulation) power supply for a cirurgical laser tool (1977-1980). The construction involved a vacuum tube cascaded with MOS-FET to obtain very high quality current source necessary for the stable characteristics of the gas discharge in the laser tube.