Triodes and Tetrodes

Richard G. Carter

doi:10.1017/9780511979231.007

6 - Triodes and Tetrodes

Published online by Cambridge University Press: 27 April 2018

Richard G. Carter

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Richard G. Carter: Affiliation:
Lancaster University

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Summary

The flow of electrons between the cathode and the anode of a diode can be controlled by introducing permeable electrodes (grids). The properties of triodes can be understood using an electrostatic model in which space-charge is neglected. The influence of the anode voltage on the electric field at the cathode is described by the penetration factor. The effects of space-charge can be included using the concept of an equivalent diode whose properties are determined by considering limiting cases. Good agreement with experimental results is obtained in this way. When the control grid is close to the cathode the emission from the cathode becomes non-uniform (island formation) and the penetration factor varies with position. It is shown that the current in a triode generally obeys the 3/2 power law but varies from this near cut-off if there is island formation. The current intercepted by the grid can be estimated by calculating electron trajectories. Similar methods can be applied to the modelling of a tetrode by reducing it to an equivalent triode. The effects of space-charge in the region between the screen grid and the anode can be understood by regarding it as a diode with injected current.

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Type: Chapter
Information: Microwave and RF Vacuum Electronic Power Sources , pp. 224 - 249

DOI: https://doi.org/10.1017/9780511979231.007 [Opens in a new window]

Publisher: Cambridge University Press

Print publication year: 2018

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