TDA1596 View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

TDA1596

IF amplifier/demodulator for FM radio receivers

Philips Electronics 

Philips Semiconductors

IF amplifier/demodulator for

FM radio receivers

Product specification

TDA1596

FUNCTIONAL DESCRIPTION

Limiter-amplifier

This has five stages of IF amplification using balanced differential limiter-amplifiers with emitter-follower coupling.

Decoupling of the stages from the voltage supply lines and an internal high-ohmic DC feed-back loop give a very stable

IF performance. The amplifier gain is virtually independent from temperature changes.

FM demodulator

The demodulator is fully balanced and comprises two cross-coupled differential amplifiers. Quadrature detection of the

FM signal is performed by feeding one differential amplifier directly from the limiter-amplifier output, and the other via an

external 90° phase-shifting network. The demodulator has good stability and its zero cross-over shift is small.

The bandwidth of the demodulator output is restricted to approximately 1 MHz by an internal low-pass filter.

THD compensation

This circuit compensates non-linearities introduced by demodulation. For this to operate correctly the demodulator circuit

between pins 9 and 10 must have a loaded Q-factor of 19. Consequently there is no need for the demodulator tuned

circuit to be adjusted for minimum THD, instead the adjustment criterium is for a symmetrical stop pulse.

Mute attenuator and AF output

The control voltage for the mute attenuator at pin 14 is generated from the values of the level detector and the detuning

detector outputs. The mute attenuator has a fast attack and a slow decay which is determined by the capacitor at pin 14.

The AF signal is passed via the mute attenuator to the output at pin 4.

A weighted control voltage, available from pin 6, is obtained from the mute attenuator control voltage via a buffer-amplifier

which introduces an additional voltage shift and gain.

Level detector

The level detector generates a voltage output which is proportional to the field strength of the input signal.

The unweighted level detector output is available when the mode switch is operating in the FM, mute-on condition.

Tuning-stop outputs

The open collector outputs STOP-0 and STOP-1 (from pins 13 and 12 respectively) are voltages derived from the

detuning level and the field strength of the input signal. If only one tuning-stop output is required, pins 12 and 13 may be

tied together.

April 1991

5

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