The vacuum electronic devices: from the origin of electronics to current applications in the high frequency field

Vacuum electronic devices were the basis of the first physical discoveries of the 19th century, starting from the low-pressure gas-filled tubes of H. Geissler in 1857 to the first vacuum tubes of W. Crookes in 1870. The Electronics started from the invention of vacuum diodes by J. A. Fleming in 1904 leading to the invention of pentodes by B. D. H. Tellegen in 1926. At the same time, gas filled tubes have founded the Power Electronics with the invention of ignitrons and thyratrons, while the classic vacuum tubes reached their latest evolution with the nuvistor series, which covered just over the Sixties of the last century. The klystrons and gyrotrons, the heirs of the microwave power vacuum tubes, are still today at the cutting edge of technology, and with these devices it is possible to reach in continuous operation powers of 1 MW at frequencies greater than 100 GHz. The article concludes with a brief overview of the state of research for new on-chip vacuum devices, which currently promise interesting applications in the high-frequency field.