Overview

The LA1143 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

1. Versatile mutings

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 40dB.

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

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

3. High S/N (78dB typ.)

4. Low distortion (0.05 typ.) available, if used with double-tuned circuits.

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

6. Signal meter drive output proportional to the input signal strength in dB (suitable to control multiplex IC LA3373).

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

8. Delayed AGC output for front end circuit.

Functions

? IF amplification/limiter

? AF preamplifier

? Signal meter output

? Muting at detuning

? Quadrature detector

? AFC output

? AGC output

? Muting at small input