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A History of the Grid

Patrick Mitchell, Electronics World, August, 2000.
    
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Cathode-Ray Amplifiers

In 1905, von Lieben constructed a cathode-ray tube with an electrode as the target. The cathode ray was steered by a magnetic field induced by coils.

Circuit diagram of the 'Kathodenstrahlenrelais' in the patent of 1906. Image courtesy hozir.org

A greater or lesser amount of the beam struck the target and thus the target current could be varied by changing the coil current. Based on his 1906 patent, the two German companies AEG and Siemens founded Telefunken AG to build Electron Tubes.

On 10 October 1906, Dieckmann and Clag of Strasbourg filed a patent for a similar device. In this alternative, variations in an electric field deflected the cathode ray such that a greater or lesser amount of it fell on a target electrode. Amplification was thus achieved by altering the proportion of cathode current striking an anode. This contrasted with the triode, in which amplification was achieved by varying the magnitude of the cathode current.

See also, Valves for single sideband generation and beam deflection valves 7360 and 6AR8.

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