LA1235

Ordering number : EN873F

FM IF System Applications

Monolithic Linear IC

SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters

TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110 JAPAN

O2097HA (KT)/63095HA (KOTO) /O076AT/8044KI, TS/4241KI/3091KI No.873-1/12

Overview

The LA1235 is a high integrated IC developed for use in

high S/N, low distortion FM IF system applications. This

IC features S/N=88dB, distortion factor=0.015% and has

almost all functions required for FM tuner IF stage.

The IF amplifier and limiter stage consist of 6 stages of

double ended differential amplifier having an excellent

AMR, and this stage is followd by the signal meter driver

which consists of 4 stages of level detector, thereby

creating extended linearity up to strong input. The FM

detector stage consists of a double balanced quadrature

detector to which a low frequency preamplifire and a

muting controller are attached. The muting drive stage

consists of an OR circuit for weak signal muting drive

output which detects signal intensity and detuning muting

drive output which detects S curve DC output and enables

the prevention of noise at the time of weak signal and

detuning. Further, the weak signal muting drive output

circuit contains a Schmitt circuit having hysteresis and

enables the prevention of muting malfunction due to

amplitude component at the time of weak signal. The AFC

output and tuning meter drive stage is of current drive type

which makes it possible to adjust AFC sensitivity and

muting band width by means of an external resistor, and

the built-in tuning meter null (short) circuit foreces the

tuning meter to be [0] when th IF amplifier stops working.

The IF amplifier stop circuit, being a circuit to stop the FM

IF amlifier at the time of AM reception, makes it possible

to decrease shock noise due to FM-AM receiving mode

switchover.

Package Dimensions

unit: mm

3006B-DIP16

[LA1235]

SANYO: DIP16

Functions

• IF amplifier, Limiter.

• Quadrature detection.

• AF preamplifier.

• Signal intesity muting drive output.

• Detuning muting drive output.

• AF signal muting circuit.

• Signal meter drive output.

• AFC, tuning meter drive output.

• IF amplifier stop circuit.

• Tunig meter null circuit.

Features

• High S/N (88dB typ.).

• Low distortion (0.015% typ.).

• Weak signal muting dirve output having hysteresis.

• Tuning mete null (short) circuit.

• Signal meter dirve output having wide dynamic range.

• High limiting sensitivity.

• Built-in constant-voltage regulated circuit (Operating

voltage : 10 to 14V).