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Audio amplifier

An audio speaker is a device that receives a signal and produces sound. The signal received by a speaker typically is an electric signal produced by an audio amplifier. The speaker receives the amplifier signal and produces vibrations which produce sound. The function of an audio amplifier is to take an input audio signal, amplify and process it as necessary, and produce an output audio signal. Audio power amplifiers have long been used to control the sound amplification, equalization, filtering, special effects, and other signal processing of the audio signal. The audio signal is generated by an audio source and then amplified and filtered by the power audio amplifier. Audio amplifiers are available in a wide assortment of design technologies, power amplification capabilities, frequency responses, enclosures, and price ranges. Audio amplifiers have been manufactured using Class A, B, and AB configurations since the earliest days of radio. A Class A amplifier is the most inefficient at delivering power to a load. Class A amplifiers have a linear region of operation, and are biased to operate from the center of the linear region of operation. A Class B amplifier is more efficient at delivering power to a load than a Class A amplifier, but adds significantly more distortion to the output signal than a Class A amplifier. Class B amplifiers have a linear region of operation that ideally passes through the turn off point of the amplifier, and are biased to operate from the turn off point. Another amplifier, known as a Class A/B, is more efficient at delivering power to a load than a Class A, and adds less distortion than a Class B. Amplifiers that are categorized as Class A/B amplifiers utilize features taken from both Class A amplifiers and Class B amplifiers. The efforts of manufacturers for reducing energy consumption, weight and size of heat sinks of consumer apparatuses, such as in the field of car entertainment, have generated a demand for power amplifiers with a greater efficiency than the traditional class AB amplifiers. Class D amplifiers have been proposed to respond to these requirements. Class D amplifiers, also known as switching amplifiers, are amplifiers that switch at a high frequency. Class D amplifiers use active power circuit elements, such as switches which are alternately driven to saturation and cut-off at a high switching speed, generating a rectangular waveform at its output. Class D amplifiers typically employ either pulse width modulation or sigma-delta modulation. Class D amplifiers are often used for audio amplification because of their power efficiency. An advantage of the Class D amplifier is that the output stage transistors are switched either completely on or completely off. Class D amplifiers provide substantially full output power, while minimizing internal power consumption. A Class D amplifier is called a "digital amplifier" because it has a feature of causing a power MOSFET to perform switching operation to drive a speaker. Generally, the purpose of a digital audio amplifier is to minimize distortion of a signal and to output high fidelity audio signals by digitally processing a received audio signal. The digital amplifier has better power efficiency than a conventional analog amplifier.

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