TERMIUM Plus^®

Fiche 1,  Justifications,  Anglais

Record number: 1, Textual support number: 1 CONT

It wasn’t until the 1980's when a new material, GaAlAs(gallium aluminum arsenide) was developed, that a rapid growth in the use of LEDs began to occur. GaAlAs technology provided superior performance over previously available LEDs. The brightness was over 10 times greater than standard LEDs due to increased efficiency and multi-layer, heterojunction type structures. The voltage required for operation was lower resulting in a total power savings. The LEDs could also be easily pulsed or multiplexed. This allowed their use in variable message and outdoor signs. LED were also designed into such application as bar code scanners, fiber optic data transmission systems, and medical equipment. Although this was a major breakthrough in LED Technology, there were still significant drawbacks to GaAlAs material. First, it was only available in a red 660nm wavelength. Second, the light output degradation of GaAlAs is greater than that of standard technology.  2, fiche 1, Anglais, - gallium%20aluminum%20arsenide

Fiche 1,  Justifications,  Français

Record number: 1, Textual support number: 1 DEF

Composé III-V ternaire, résultant de la combinaison de l'arsenic, du gallium et de l'aluminium, utilisé comme semi-conducteur dans la fabrication de composants optoélectroniques.  1, fiche 1, Français, - ars%C3%A9niure%20d%27aluminium%20et%20de%20gallium

Fiche 1,  Justifications,  Espagnol

Fiche 2,  Justifications,  Anglais

Record number: 2, Textual support number: 1 CONT

High-power modulation. In an AM transmitter amplitude modulation of the carrier by introducing the modulating signal into the anode circuit of the final amplifying stage. The power of the modulating signal thus approximates to that at the transmitter output.  5, fiche 2, Anglais, - high%2Dpower%20modulation

Record number: 2, Textual support number: 2 CONT

Modulation is also identified as to level. High level modulation occurs when the modulating voltage is applied to the collector/plate circuit of the final power amplifier. With high level modulation, the final stage is operated class C and the preceding stages are also operated class C. The overall efficiency of such a transmitter is very high. A disadvantage of high level modulation is that comparatively high audio power is needed and several stages of voltage and power amplification may be required in the speech amplifier and modulator circuits.  4, fiche 2, Anglais, - high%2Dpower%20modulation

Fiche 2,  Justifications,  Français

Fiche 2,  Justifications,  Espagnol

Record number: 2, Textual support number: 1 DEF

Modulación de la portadora de un transmisor de radio efectuada en el amplificador de radiofrecuencia final, normalmente en su circuito anódico.  1, fiche 2, Espagnol, - modulaci%C3%B3n%20a%20alto%20nivel

Fiche 3,  Justifications,  Anglais

Record number: 3, Textual support number: 1 DEF

[The] operation of an active device in which the bias and signal amplitude are so chosen that output current flows throughout each cycle of input signal (assumed sinusoidal), i.e. the angle of flow is 360°.  3, fiche 3, Anglais, - class%2DA%20operation

Record number: 3, Textual support number: 1 CONT

Class-A operation. Class-A amplifier operation is characterized by a conduction period of the output current(collector or drain) of 360°. That is, the operating point is chosen to have a constant voltage and current. In effect, the amplifier power is on all the time. This is referred to as linear operation. By operating in the linear region of the transistor's characteristics, the amplified signal suffers minimum distortion. This comes at a price of inefficiency in the amplifier. The theoretical maximum possible efficiency of a class-A amplifier is 50%, but due to linearity requirements of the applications, the efficiency may be no more that 25%.  4, fiche 3, Anglais, - class%2DA%20operation

Fiche 3,  Justifications,  Français

Fiche 3,  Justifications,  Espagnol