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Fleming went on to develop a two-element thermionic vacuum tube diode called the Fleming valve (patented 16 November 1904). [24] [25] [26] Thermionic diodes can also be configured to convert a heat difference to electric power directly without moving parts as a device called a thermionic converter, a type of heat engine.
A variety of silicon diodes of different current ratings. At left is a bridge rectifier. On the 3 center diodes, a painted band identifies the cathode terminal. Silicon diodes are the most widely used rectifiers for lower voltages and powers, and have largely replaced other rectifiers. Due to their substantially lower forward voltage (0.3V ...
The Schottky effect or field enhanced thermionic emission is a phenomenon in condensed matter physics named after Walter H. Schottky. In electron emission devices, especially electron guns , the thermionic electron emitter will be biased negative relative to its surroundings.
A thermal diode in this sense is a device whose thermal resistance is different for heat flow in one direction than for heat flow in the other direction. I.e., when the thermal diode's first terminal is hotter than the second, heat will flow easily from the first to the second, but when the second terminal is hotter than the first, little heat will flow from the second to the first.
The thermionic diode was later widely used as a rectifier — a device that converts alternating current (AC) into direct current (DC) — in the power supplies of a wide range of electronic devices, until beginning to be replaced by the selenium rectifier in the early 1930s and almost completely replaced by the semiconductor diode in the 1960s ...
Rectifiers (diodes) [ edit ] Hydrogen can be removed from individual tetraphenylporphyrin (H 2 TPP) molecules by applying excess voltage to the tip of a scanning tunneling microscope (STAM, a); this removal alters the current-voltage (I-V) curves of TPP molecules, measured using the same STM tip, from diode -like (red curve in b) to resistor ...
A thermionic diode is a thermionic-valve device consisting of a sealed, evacuated glass or metal envelope containing two electrodes: a cathode and a plate. The cathode is either indirectly heated or directly heated. If indirect heating is employed, a heater is included in the envelope.
All practical thermionic converters to date employ caesium vapor between the electrodes, which determines both the surface and plasma properties. Caesium is employed because it is the most easily ionized of all stable elements. A thermionic generator is like a cyclic heat engine and its maximum efficiency is limited by Carnot's law.