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Application Report
SLOA043 - December 1999
1
A Low-Cost, Single Coupling Capacitor Configuration for
Stereo Headphone Amplifiers
Shawn Workman AAP Precision Analog
ABSTRACT
This application report compares two possible blocking or coupling capacitor configurations
for stereo headphone amplifiers operating from a single supply voltage. The report
demonstrates that the standard two-capacitor configuration can be replaced by a
single-capacitor configuration with little or no perceivable difference in sound quality. The
primary advantage of a single-capacitor system is that only one large capacitor is required.
In many compact multimedia systems like those in personal digital audio players, wireless
phones, and personal digital assistants (PDA), these capacitors can be the largest
components on the board. Therefore, eliminating one of the bulky coupling capacitors
reduces cost and minimizes the area needed on the circuit board.
Contents
Effect of Coupling Capacitors 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coupling Capacitor Circuits 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Effect of Crosstalk on Sound Quality 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Test Measurements 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Selecting the Single Coupling Capacitor 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Summary 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
List of Figures
1 Standard Headphone Jacks 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 TPA102 Audio Amplifier-Dual Capacitor Configuration 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 TPA102 Audio Amplifier-Single Capacitor Configuration 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Single Capacitor Equivalent Circuit Model 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 Crosstalk vs Frequency for a 32-Ω-Load and a 330-µF-Coupling Capacitor 4. . . . . . . . . . . . . . . . . . . . .
6 Crosstalk vs Frequency for a 10-kΩ-Load and a 330-µF-Coupling Capacitor 5. . . . . . . . . . . . . . . . . . . .
7 Lab Setup for the TPA102 EVM 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8 Crosstalk Measurement of Single Capacitor Configuration 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
List of Tables
1 Common Load Impedance vs Low Frequency Output Characteristics 2. . . . . . . . . . . . . . . . . . . . . . . . . .
