LM1894

General Description

The LM1894 is a stereo noise reduction circuit for use with

audio

playback

systems.

The

DNR

system

is

non-complementary, meaning it does not require encoded

source material. The system is compatible with virtually all

prerecorded tapes and FM broadcasts. Psychoacoustic

masking, and an adaptive bandwidth scheme allow the DNR

to achieve 10 dB of noise reduction. DNR can save circuit

board space and cost because of the few additional compo-

nents required.

Features

n Non-complementary noise reduction, “single ended”

n Low cost external components, no critical matching

n Compatible with all prerecorded tapes and FM

n 10 dB effective tape noise reduction CCIR/ARM

weighted

n Wide supply range, 4.5V to 18V

n 1 Vrms input overload

Applications

n Automotive radio/tape players

n Compact portable tape players

n Quality HI-FI tape systems

n VCR playback noise reduction

n Video disc playback noise reduction

Typical Application

Trademark and license agreement required for use of this product.

DS007918-1

*R1+R2 = 1k

Ω total.

See Application Hints.

Order Number LM1894M or LM1894N

See NS Package Number M14A or N14A

FIGURE 1. Component Hook-Up for Stereo DNR System

December 1994

© 1999 National Semiconductor Corporation

DS007918

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