Tuesday, August 11, 2009
LM1894 Dynamic Noise Reduction System DNR
INTRODUCTION
The operating principles of a single-ended or non-complementary audio noise reduction system, DNR, have been covered extensively in a previous application note AN384, Audio Noise Reduction and Masking. Although the system was originally implemented with transconductance amplifiers (LM13600) and audio op-amps (LM387), dedicated I/Cs have since been developed to perform the DNR function.
The LM1894 is designed to accommodate and noise reduce the line level signals encountered in video recorders, audio tape recorders, radio and television broadcast receivers, and automobile radio/cassette receivers. A companion device, the LM832, is designed to handle the lower signal levels available in low voltage portable audio equipment. This note deals chiefly with the practical aspects of using the LM1894, but the information given can also be applied to the LM832.
THE BASIC DNR APPLICATION CIRCUIT
At the time of writing, the LM1894 has already found use in a large variety of applications. These include:
AUTOMOTIVE RADIOS
TELEVISION RECEIVERS
HOME MUSIC CENTERS
PORTABLE STEREOS (BOOM BOXES)
SATELLITE RECEIVERS
AUDIO CASSETTE PLAYERS
AVIONIC ENTERTAINMENT SYSTEMS
HI-FI AUDIO ACCESSORIES
BACKGROUND MUSIC SYSTEMS
ETC.
The operating principles of a single-ended or non-complementary audio noise reduction system, DNR, have been covered extensively in a previous application note AN384, Audio Noise Reduction and Masking. Although the system was originally implemented with transconductance amplifiers (LM13600) and audio op-amps (LM387), dedicated I/Cs have since been developed to perform the DNR function.
The LM1894 is designed to accommodate and noise reduce the line level signals encountered in video recorders, audio tape recorders, radio and television broadcast receivers, and automobile radio/cassette receivers. A companion device, the LM832, is designed to handle the lower signal levels available in low voltage portable audio equipment. This note deals chiefly with the practical aspects of using the LM1894, but the information given can also be applied to the LM832.
THE BASIC DNR APPLICATION CIRCUIT
At the time of writing, the LM1894 has already found use in a large variety of applications. These include:
AUTOMOTIVE RADIOS
TELEVISION RECEIVERS
HOME MUSIC CENTERS
PORTABLE STEREOS (BOOM BOXES)
SATELLITE RECEIVERS
AUDIO CASSETTE PLAYERS
AVIONIC ENTERTAINMENT SYSTEMS
HI-FI AUDIO ACCESSORIES
BACKGROUND MUSIC SYSTEMS
ETC.
MORE......http://www.national.com/ds/LM/LM1894.pdf
Thursday, August 6, 2009
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