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The control grid is an electrode used in amplifying thermionic valves (vacuum tubes) such as the triode, tetrode and pentode, used to control the flow of electrons from the cathode to the anode (plate) electrode. The control grid usually consists of a cylindrical screen or helix of fine wire surrounding the cathode, and is surrounded in turn by ...
The mutual conductance tester tests the tube dynamically by applying bias and an AC voltage to the control grid, and measuring the current obtained on the plate, while maintaining the correct DC voltages on the plate and screen grid. This setup measures the transconductance of the tube, indicated in micromhos. [3]
Plate detector circuit with cathode bias. Cathode bias RC time constant three times period of lowest carrier frequency. C L is typically around 250 pF.. In electronics, a plate detector (anode bend detector, grid bias detector) is a vacuum tube circuit in which an amplifying tube having a control grid is operated in a non-linear region of its grid voltage versus plate current transfer ...
The control grid of the variable-mu pentode is constructed so as to result in a given incremental change of control grid voltage having less effect on change of anode current as the control grid voltage increases negatively relative to the cathode. [7] The control grid often has the form of a helix of varying pitch. [8]
Grid leak detection optimized for operation in this region is known as power grid detection or grid leak power detection. [29] [30] Grid current occurs only on the positive peaks of the carrier frequency cycle. The coupling capacitor will acquire a dc charge due to the rectifying action of the cathode to grid path.
The first grid, known as the control grid, (and sometimes other grids) transforms the diode into a voltage-controlled device: the voltage applied to the control grid affects the current between the cathode and the plate. When held negative with respect to the cathode, the control grid creates an electric field that repels electrons emitted by ...
The space charge grid tube was the first type of tetrode to appear. In the course of his research into the action of the audion triode tube invented by Edwin Howard Armstrong and Lee de Forest, Irving Langmuir found that the action of the heated thermionic cathode was to create a space charge, or cloud of electrons, around the cathode. <confused: de Forest invented the triode, Armstrong gave a ...
Alternatively, the cathode may short to the control grid, possibly causing similar effects, or, the control grid and screen grid (G2) [225] can short causing a very dark image or no image at all. The cathode may be surrounded by a shield to prevent sputtering. [226] [227]