Research: Class D Amplifier Solutions & Practical Considerations
Fall 2009

OBJECTIVE:  To research common switching (class D) amplifier design techniques and their implementation in various consumer applications. 

RESEARCH SUMMARY:  Class-D_amp_research.pdf  (21 pages)

NOTE:  The above document is only a rough outline summarizing key information from my research.  I had hoped to produce a well-written report; however, the breadth of my research would’ve required a 50+ page paper which I regretfully did not have time to write.  Nonetheless, this outline provides a useful summary of my research on Class D amplifier design and implementation. 


Research Emphasis:
    - Class D amplifier topologies
    - Common applications
    - Tradeoffs between switching amps & linear amps
    - Practical considerations when designing & implementing switching amplifier solutions
    - Emerging device technologies

Specific Topics:

·      Class D history

·      Class D topologies & modulation techniques

·      Output filter vs. filterless topologies

·      Output switching circuits (half-bridge vs. H-bridge)

·      Sources of distortion in class D amps

·      EMI & noise considerations

·      Thermal considerations

·      PCB layout considerations

·      Power supply requirements & considerations

·      Typical class D solutions for:

o   Low power mobile applications

o   High power applications

o   High fidelity applications

REFERENCES:  Interested readers are encouraged to review the extensive list of online references (below) gathered during my research.

Click HERE for the printable list.



Eli Hughes, resident expert on switching amplifiers (Penn State University Audio Engineering Society)


NEWS - Miscellaneous

Class D Amplifiers Empower Mobile Multimedia

Designing With Class D Amplifier ICs





International Rectifier
List of IRF application notes on class D


Class D Audio Amplifier Basics

A Class D audio amplifier is basically a switching amplifier or PWM amplifier. There are a number of different classes of amplifiers. This application note takes a look at the definitions for the main classifications.


Class D Audio Amplifier Performance Relationship to MOSFET Parameters

This application note discusses key parameters to be considered in the selection of MOSFETs for class D audio amplifier and their relationship with amplifier’s performance such as efficiency, EMI, and THD. In addition, benefits and advantages of IR Digital Audio MOSFETs in class D audio amplifier are presented.


PCB Layout with IR Class D Audio Gate Drivers

…The layout of a class D amplifier remains the most obscure part of the design process. The purpose of this application note is to highlight aspects of the PCB layout which require a designer’s careful attention.


IRS2092(S) Functional Description

The IRS2092(S) is a Class D audio amplifier driver with integrated PWM modulator and over current protection. Combined with two external MOSFETs and a few external components, the IRS2092(S) forms a complete Class D amplifier with dual over current, and shoot-through protection, as well as UVLO protection for the three bias supplies.


IRS2093M Functional Description

The IRS2093M is a four channel Class D audio amplifier driver with integrated PWM modulators and over current protection. Combined with eight external MOSFETs and external passive components, the IRS2093M forms four complete Class D amplifiers.



National Semiconductor


Class D Amplifier FAQ

This FAQ is intended to capture a variety of knowledge about the selection, application, and measurement of Class D amplifiers. The emphasis of this FAQ is towards Class D amplifiers in the 0.5W to 2W range intended for portable media devices such as mobile phones, portable DVD players, and portable navigation systems. However, the vast majority of this information can be applied to Class D amplifiers from milliwatts to kilowatts of output power.




Rane Corporation


Commercializing Class D Amplifier Technologies

The popularity of commercial audio systems having large numbers of channels has resulted in a growing demand for smaller, lighter, and less expensive multichannel power amplifier products. This paper describes how careful integration of power factor corrected switchmode power supplies, class D power amplifiers, and digital signal processors yields high power density and especially reliable and electromagnetically quiet products at a reasonable cost.




Elliott Sound Products

(Professional results for the Do-It-Yourself enthusiast)


Class D Audio Amplifiers - Theory and Design



Minimize Noise in Audio Channels with Smart PCB Layout

Class D Amplifiers: Fundamentals of Operation and Recent Developments

Thermal Considerations for a Class D Amplifier

Reference Design for a Class-D, 2.1 Channel, Audio Amplifier for an MP3 Player Docking Station

Overview of 2.1 (Satellite/Subwoofer) Speaker Systems
                - for 2.1 stereo PC speakers

Spread-Spectrum-Modulation Mode Minimizes Electromagnetic Interference in Class D Amplifiers
                - no output filter needed in class D!

Reduce EMI from Class D Amplifiers Using New Modulation Techniques and Filter Architectures

Feature-Rich, Complete Audio Record/Playback for GSM/GPRS Cell Phones

Class D Audio Amplifiers Save Battery Life – 2002

Class D Audio Amplifier Output Filter Optimization – 2002

Amplifier Considerations in Ceramic Speaker Applications - (pg 3-6)

Class G and Charge-Pump Technologies Maximize Efficiency in Boosted Amplifiers with Minimal Support Components
                - class D cannot drive ceramic (piezoelectric) speakers

Circuit Refinements Ensure Quality Audio in Portable Devices


National Semiconductor

Personal Mobile Devices – Selection Guide

Analog Product Guide 2009 Vol 2

Filterless Class D Amplifiers

Managing EMI in Class D Audio Applications

Noise, TDMA Noise, and Suppression Techniques

LM49352 - Mono Class D Audio Codec Subsytem with Ground Referenced Headphone Amplifiers, Earpiece Driver, and Audio DSP from the PowerWise® Family

National Semiconductor Extends Family of Low-Power, Premium Quality Audio Subsystems for Handheld Devices,1735,1390,00.html

App Notes:

LM48511 - 3W, Ultra-Low EMI, Filterless, Mono, Class D Audio Power Amplifier with Spread Spectrum

National Semiconductor’s New Audio Amplifier with Spread Spectrum and Integrated Boost Architecture Reduces EMI Sensitivity in Portable Applications,1735,1288,00.html

Reference Design 167 - High Efficiency Portable Media Player (PMP) Docking Station

LM4962 Stereo Ceramic Speaker Driver Application Note
                - not class D


National Semiconductor NEWS:

2009 - National Semiconductor’s New Stereo Headphone Amplifier Doubles Audio Playback Time for Portable Devices,1735,1391,00.html
                - class G amp

2004 - National Semiconductor Introduces Two High Efficiency Class D Boomer Audio Amplifiers for Cellular Phones and Flat Panel Monitors,1735,957,00.html
                - one of these amps is obsolete


Analog Devices

Class D Audio Amplifiers:  What, Why, and How


Stereo Audio Codecs Deliver Best Audio Experience with Lowest Power Dissipation



D2Audio® DAE-1: D2-814xx PWM Controllers – The World’s First Intelligent Digital Amplifier Solution

Reference Design
D2AUDIO® TXF15-2 – Advanced Audio Processing Solution for Stereo, 2.1 and Bi-Amp TV’s


Audio Engineering Society

Call for comment on reaffirmation of AES17-1998


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