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Vacuum Tube

Introduction

Vacuum tube - electronic device consisting of electrodes placed in the bulb of air (vacuum tube) or a gas at low pressure (flash gas), which uses a beam of electrons or ions moving between the electrodes and electrically operated lamp electrodes. It can be used among other things to strengthen, generation and conversion of electrical signals. Tubes are one of the many electronic elements active, historically the first.

In 1897, Joseph John Thomson examined the effect of the electric field and magnetic flux on electrons. His work led to the discovery of the electron and was awarded the Nobel Prize in Physics in 1906. In 1904, John Ambrose Fleming built the first vacuum tube - LED. The first lamp strengthening triode developed in 1907, Lee De Forest. Irving Langmuir working for General Electric in the years 1909 - 1916 a much improved and invented the technique of vacuum diffusion pump , which enabled the achievement of high vacuum and significantly improved performance tubes. Langmuir developed the basic theory of electron tubes, which had a big impact on their later development. In 1923 he was in Caernarvon first tube high power radio transmitter, contained 48 parallel tubes with a capacity of 600 each.

Discussion

The basic criterion for classification tubes is the gas pressure in the bulb. Thus, the lamp is divided into, vacuum and carbonated. It shall also apply to the division for the intended use, for example, rectifiers, detection, strengthening, generational, mixing, photoelectric, imaging, memory, etc. Because of the frequency range can be divided into low-frequency light (acoustic frequency range), high frequency (radio frequency range) and microwave (above 300 MHz). He meets a small division of lamps and high power. The dividing line ran generally about permissible power dissipated at the anode equal to 25W. Often used is the division of the number of electrodes: LED (2 electrodes), triode (3 electrodes), tetrode (4 electrodes), pentode (5 electrodes), heksoda (6 electrodes), heptoda (7 electrodes), etc.

Due to the nature of the cathode lamps can be divided into: cold cathode lamps, with a photocathode, indirectly-heated cathode (isolated heater placed in the tube cathode) and the directly-heated cathode (cathode in the form of annealed wire). Depending on the parameters of glow lamps were produced in "batches" to allow the use of a common power source for many of the filament lamp. In practical applications, it is important to the type of lamp base. He meets a number of additional terms describing their lamps traits (e.g., pulse - the pulse, Electrometric - with small leakage current grid), the degree of miniaturization, a value, type of enclosure, cooling method, etc. The particular lamp can of course be determined by various combinations of, for example: gas pulse tetrode, indirect high frequency triode annealed etc.

Low Power Vacuum Tubes

In the vacuum tubes is the residual gas pressure of less than 10 -6 ... 10 -8 Torr. The presence of gas when there is no effect on the values ??of currents, the electric charge carriers ...