Abstract :
In this work a historical description of the development process of electronics in its first part, the thermionic age, is made. The contributions of the three main authors are described that gave origin to the same one: Edison, Fleming and De Forest. The contribution made by the physics is also described and we propose some important developments in its time of maturity like the tetrodo, pentodo, thyratrón, magnetrón and the klystron. In all cases it is given a brief technical description of the same accompanied by the historical information related with the date and authors of each development. We also propose, in brief form, the role of the vacuum tubes at the present time.