TEA7532DP datasheet(7/16 Pages) STMICROELECTRONICS

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Amplifier dc supply.

In transmission mode, the supply voltage is control-

led by the internal shunt DC regulator. For this rea-

son, the TEA7532 should be supplied from a current

source

(see : supply considerations).

An antidistortion system is embodied which pro-

vides AGC control to avoid loudspeaker distortion

under current-limited conditions.

Figure 13.

Circuit action.

When the supply voltage is insufficient, the voltage

at pin 1, falls below the reference voltage 1.1 V, re-

sulting in transistor (TR) being switched off, resulting

in zero current flow in resistor R. This state enables

the gain control system. Under these conditions, the

shunt DC supply will switch at a rate determined by

the time constant of the RC network on pin 3.

This switching action accomodates normal speech

characteristics under low supply conditions.

1.2. ANTIACOUSTIC FEED-BACK SYSTEM (AN-

TILARSEN SYSTEM)

The purpose of this system is to control AGC action

in order to avoid acoustic feed-back between the

loudspeaker and the microphone, when used in a

telephone set.

Figure 14 .

TEA7532

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