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a device used to increase the power of electric signals. Since the amplified signals are variations in time, or oscillations, of voltage or current, a signal amplifier is, essentially, an amplifier of electric oscillations.
Signal amplifiers may be divided into such classes as low-or high-frequency amplifiers, video amplifiers, and DC amplifiers. Signal amplifiers also include instrument amplifiers, which are used as components of such measurement apparatus as electronic voltmeters, oscilloscopes, potentiometers, and instruments that use bridges. An instrument amplifier makes possible increased sensitivity and accuracy in the measurement of both electrical and nonelectrical quantities. The primary requirement of such an amplifier—that it provide a fixed gain—is satisfied owing to its large amount of negative feedback. Moreover, in a number of instruments, such as voltmeters and oscilloscopes, the amplifier must ensure normal operation of the instrument over a wide frequency range that sometimes extends from zero to several gigahertz.
G. V. VOISHVILLO