Overview

The LA1140 is an IF system IC designed for FM car stereo receivers. It features versatile muting characteristics and allows receiver designers to realize the muting performance according to their design concept. Since the muting characteristics can be varied with a switch or a semi-fixed resistor, DX-Local switching will be accomplished with ease.

特性 Features

? Versatile muting

a) When muting operation is performed under a weak signal strength, an attenuation slope of the audio output against the input signal strength variations can be set at any given value.

b) Maximum muting attenuation can be selected to be approximately 6 to 40 dB.

c) Input signal strength level which actuates the muting circuit can be set freely.

? High limiting sensitivity (25 dBμ typ. with muting off) provides a fine quieting characteristic.

? High S/N (78 dB typ.)

? Low distortion (0.05 typ.) avaiable if used with double-tuned circuits.

? Good AMR (63 dB typ. with 6 stages of differential IF amplifiers).

? Signal meter drive output proportional to the input signal

strength in dB (suitable to control multiplex IC LA3370).

? Clamped (±VBE) AFC output, bandwidth adjustable.

? Delayed AGC output for front end circuit.

? Small space factor due to single-ended package employed.

? 3 mm pitch of pin terminals permitting ease-to-write PC board pattern.

Functions

? IF amplification/limiter

? Quadrature detector

? AF preamplifier

? AFC output

? Signal meter output

? AGC output

? Muting bandwidth

? Muting under weak signal strength