Design of audio amplifiers: selection guide for Class-D audio amplifier and circuit ideas
If you already know about class A, B, and AB, they are all linear amplifiers with constant gain where the audio is fed to the base of a transistor. The latest class D audio amplifier is switch type amplifier by using Pulse Width Modulator (PWM) amplifier. In class A, B and AB type amplifiers which are linear amplifiers, the gain is constant irrespective of bus voltage variations but the gain is proportional in class D amplifiers. Class D amplifiers are much efficient than linear amplifiers.
The lower power consumption of Class D amplifiers make them suitable for audio amplifier design. Class D is more relevent for battery operated devices such as phones and notebooks, netbooks and tablets due to low power consumption.
Class D amplifier market: Due to the power performance of Class D amplifiers, its market is growing around 20- 30% on average.
Drawback: The drawback of class D amp is, switching of the outputs in the Class D amplifiers causes EMI and hence in most applications which require EMI certification need to be dealt cautiously.
Class D amplifiers are used in designing audio amplifiers in many applications, including powered subwoofers, powered speakers, mobile applications (to save battery power), and bass amplifiers.
Here below we provide a list of class D amplifiers from leading semicoductor vendors.
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Author: Srinivasa Reddy N