Objective:

Provide a better understanding of coupling capacitors and how to eliminate them from an audio applications.

Online Seminar:

High-Performance Audio Amplifiers for Portable Applications, 4/29/02, Kevin Hoskins
This presentation will acquaint you with recent additions to National Semiconductor Corporation's Boomer® family of headphone and speaker audio amplifiers. Also discussed is new technology that eliminates the old fashioned coupling capacitors used with headphones. We will also review package technologies that minimize PCB area and maximize thermal efficiency

Reading Assignment:

For a better understanding of coupling capacitors and their usage, read the application section for the LM4910.

Additional Resources:

• Review online seminar presentation. (ppt: 1.9MB)   
• For additional information, consult the Knowledge Base using the following key words:
  • BTL     
  • Headphone Amplifiers     
  • LLP

Research Assignment:

• Traditional stereo headphone amplifiers use coupling capacitors between their outputs and the speakers.  Together, the value of the coupling capacitor and the speaker's resistance creates the cutoff frequency of a high pass filter.  Refer to the seminar to determine the following:
  • If R_L=24 Ohms and the desired frequency response extends to 30Hz, what is the value of C_coupling? (Round to nearest µF) check answer 
  • R_L=8 Ohms and the frequency response extends to 30Hz, what is the value of C_coupling? (Round to nearest µF) check answer  
• The LM4867 is available in National Semiconductor Corporation's 24 pin leadless lead frame package (LLP).  When comparing this package to the traditional solution's 24 pin TSSOP, how much board space is saved by using the 24-pin LLP? (in percent) check answer     
• The LM4910 eliminates output coupling capacitors.  Using the online seminar describe how is this achieved?  Why does this work? check answer

Program Coordinator/Professor

Kevin Hoskins has been a Staff Applications engineer since 1984. He wields his soldering iron at National Semiconductor Corporation's Audio Products Group in Santa Clara, California.  He has also performed application duties with the Data Acquisition Products Group at National Semiconductor Corporation also in Santa Clara, California.

Quiz:

Take a quiz to check your understanding of this subject. Click here.
Answer all questions correctly to receive a certificate from Dean Bob Pease.