功率放大的英文文章

百度一下 或是 维基百科 “amplifier ”

Generally, an amplifier or simply amp, is any device that changes, usually increases, the amplitude of a signal. The "signal" is usually voltage or current. The relationship of the input to the output of an amplifier — usually expressed as a function of the input frequency — is called the transfer function of the amplifier, and the magnitude of the transfer function is termed the gain.

In popular use, the term usually refers to an electronic amplifier, often as in audio applications to operate a loudspeaker that is being used in a PA system to make the human voice louder or play recorded music. Amplifiers may be classified by the input (source) they are designed to amplify (such as a guitar amplifier to perform with an electric guitar), or named for the device they are intended to drive (such as a headphone amplifier), or by the frequency range of the signals (Audio, IF, RF and VHF amplifiers for example), or grouped by wheth