Class D audio amplifier, also named switch amplifier, is used to transform the input analog audio signal or PCM digital information into pulse signal of PWM or PDM, and to control large power switch device to put through/cut off audio power amplifier.

The theoretical efficiency of class A audio amplifier is 25%, and its real efficiency is about 15-20%; the theoretical efficiency of class B is about 75%; the theoretical efficiency of class AB is about 75% as well with a real efficiency between 50%-70%; the theoretical efficiency of class D is about 100% with a real efficiency of more than 85%. The high efficiency of class D offers lots of advantages, such as power saving, which is quite important for MP3 and music mobile phones. Power saving means longer paying time, and can attract more clients. Another advantage is a smaller heat generation, which can reduce heat management costs. For instance, large power class AB amplifiers usually need radiator, but the as powerful class D amplifiers do not need it.

    Efficiency Contrast between Class D Audio Amplifier and Class AB Audio Amplifier

The class D audio amplifier circuit is has a comparably smaller size. Besides, under most conditions, it does not need any heat sinks; therefore, the entire size can be reduced greatly. It is quite important for car audio and mobile phone due to the strict size requirements.

Currently, there are 108 varieties of class D audio IC. The above figure is the product classifications and shares for each manufacturer. The audio amplifier IC markets, which are sensitive to volume, efficiency etc, such as mobile phones, portable audio/video players, flat screen televisions, projection televisions, car audios, notebook computers etc, are all the potential markets of class D audio amplifier IC.

Class D audio amplifier IC also has many disadvantages such as EMI (Electro Magnetic Interference), distortion, narrow frequency response rage, narrow dynamic range, high power requirements and costs, etc.

Considering the mobile phone market, the major problems are EMI and cost. However, this market adopts platform strategy; and it is impossible to enter the market solely relying on class D audio amplifier IC. Therefore, the professional manufacturers of class D audio IC should aim at the markets of flat screen television, car audio and multi-channel audio. Considering those markets, the major problems are cost and timbre, especially the timbre.  ¦¤-¦² should be used to improve the timbre. And ADI could be the best choice.

The class D audio amplifier circuit is has a comparably smaller size. Besides, under most conditions, it does not need any heat sinks; therefore, the entire size can be reduced greatly. It is quite important for car audio and mobile phone due to the strict size requirements.

Currently, there are 108 varieties of class D audio IC. The above figure is the product classifications and shares for each manufacturer. The audio amplifier IC markets, which are sensitive to volume, efficiency etc, such as mobile phones, portable audio/video players, flat screen televisions, projection televisions, car audios, notebook computers etc, are all the potential markets of class D audio amplifier IC.

Class D audio amplifier IC also has many disadvantages such as EMI (Electro Magnetic Interference), distortion, narrow frequency response rage, narrow dynamic range, high power requirements and costs, etc.

Considering the mobile phone market, the major problems are EMI and cost. However, this market adopts platform strategy; and it is impossible to enter the market solely relying on class D audio amplifier IC. Therefore, the professional manufacturers of class D audio IC should aim at the markets of flat screen television, car audio and multi-channel audio. Considering those markets, the major problems are cost and timbre, especially the timbre.  ¦¤-¦² should be used to improve the timbre. And ADI could be the best choice.

2. Class D Audio IC Industry
2.1 Development of class D audio IC
2.2 Example of class D audio amplifier IC for mobile phone application
2.3 Application status of class D audio amplifier IC

3. Class D Audio Amplifier IC Market
3.1 Music mobile phone market
3.3 Portable audio/video player
3.4 Car audio
3.5 Flat screen television
3.6 Home audio system
3.7 PC Multi-media audio 

4. Audio IC Manufacturers
4.1 YAMAHA
4.2 TI
4.3 National Semiconductor
4.4 Maxim
4.5 On Semiconductor
4.6 Philip
4.7 Microsemi
4.8 ST
4.9 CIRRUS
4.10 ADI
4.11 WOLFSON
4.12 New Japan Radio
4.13 ZETEX
4.14 AT CHIP
4.15 Monolithic Power
4.16 SIGMATEL
4.17 Power Analog Microelectronics
4.18 Tripath