Class D amplifier

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class D amplifier

[‚klas ′dē ′am·plə‚fī·ər]
A power amplifier that employs a pair of transistors that are connected in push-pull and driven to act as a switch, and a series-tuned output filter, which allows only the fundamental-frequency component of the resultant square wave to reach the load.

Class D amplifier

An audio amplifier that works in the digital domain. It generates the equivalent analog output for the speakers by using pulse width modulation (PWM) or pulse density modulation (PDM) rather than the traditional digital-to-analog conversion. See PWM and PDM.

Less Heat than Analog
Because pulse modulation output signals are either on or off, Class D amplifiers produce far less heat than analog amplifiers. Reaching efficiencies greater than 90% compared to only 50% for analog, they are widely used for every amplification requirement from cellphone speakers to high-end stereos.

Digital and Analog
Class D was not coined for "digital;" it was the next letter after Class C. However, it does produce a "digital-like" output because the signals are generated by turning a switch fully on or off. But it is not technically digital because the output is not digital data. It is a modulated audio signal that is feeding analog speakers and is equivalent to the output of a traditional analog amplifier. Some call this a "synthesized analog" output. See amplifier classes.
References in periodicals archive ?
The Si270x Class D amplifier is designed to be combined seamlessly with Silicon Labs' popular Si473x AM/FM radio tuner products to enable complete consumer audio platform solutions.
Traditionally, Class AB amplifiers have been widely used in the audio industry, but Class D amplifiers were limited to applications such as mini-systems and DVD receivers where high fidelity was a second priority to form factor.
According to a report published by the semiconductor industry analyst, Steve Sziron at Inside Chips, "The technology matches the sound quality of analog amps and the size and low heat generation of Class D amplifiers, and is sufficiently inexpensive to go into mass market applications.
The TDA892x family of Class D amplifiers will have particular value for DVD receivers and lifestyle micro systems, where space is very limited.
Most Class D amplifiers employ pulse width modulation (PWM), typically operating at a switching rate of hundreds of kilohertz to achieve the required system performance.
Measurement results are made possible by JamTech's innovative sub-ranging PWM digital amplifier architecture that inherently avoids the fundamental distortion mechanism of traditional Class D amplifiers.
ADI's SSM2301 and SSM2304 Class D amplifiers are designed to efficiently drive speakers in handheld and portable consumer applications by consuming minimal power, employing sigma-delta modulation to reduce electromagnetic interference (EMI) emissions, and integrating a filterless topology that eliminates external components.
For instance, large power class AB amplifiers usually need radiator, but the as powerful class D amplifiers do not need it.
JAM Singapore will be fully staffed for IC design, manufacturing operations, applications engineering and sales, to support increasing demand for the new JAM True Fidelity digital Class D Amplifiers.