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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]
The suppressor grid is usually operated at or near the potential of the cathode and prevents secondary emission electrons from the plate from reaching the screen grid. [ 4 ] [ 5 ] The addition of the suppressor grid permits much greater output signal amplitude to be obtained from the plate of the pentode in amplifier operation than from the ...
Alternatively, the cathode may short to the control grid, possibly causing similar effects, or, the control grid and screen grid (G2) [227] can short causing a very dark image or no image at all. The cathode may be surrounded by a shield to prevent sputtering. [228] [229]
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 screen voltage is the same, at 300, but its dissipation rises to 3.5 watts. 37 watts of R.F. power is produced from 220 mW of drive but only a 50% duty cycle is allowed. The maximum allowable negative control grid, g1 excursion allowable is -200 volts and average control grid current is 5mA in both A.M. and CW modes. [ 1 ]
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 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 ...