An introduction to amplifiers.
Amplifier Amplifier, a device for increasing the magnitude of some quanity and, as normally used, applies to a transistor or vacuum tube and an associated citcuit arranged to reproduce a greater magnitude of voltage or current. Amplifiers are classed in various way according to their use, but all types depened on a few basic circuits. In any vacuum-tube amplifire circuit the fundamental operation is the contolling of the plate current by a voltage applied to the grid.
In the junction transistor amplifier circuit with a grounded emitter, voltage appliedto the base-emitter circuit controlas the amplification in the collector circuit. Amplifiers have a wide variety of applications. In the ordinary radio recervier there are usaully several stages of tuned amplifiers handiling the high-frequency singal before detection, then one or more audio voltage amplifiers, resistance- or transformercoupled, and a power amplifier to drive the loudspeacker. Phonographs and public address systems are other appliacations of audio amplifiers. Radio and television stations use a wide variety of amplifiers.
