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TEA1114AT/C1 View Datasheet(PDF) - Philips Electronics

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Description
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TEA1114AT/C1 Datasheet PDF : 28 Pages
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Philips Semiconductors
Low voltage telephone transmission circuit with
dialler interface and regulated strong supply
Product specification
TEA1114A
Receiving stage (pins IR, RX, GAR and QR)
The receive part consists of a receive amplifier and an
earpiece amplifier.
THE RECEIVE AMPLIFIER (PINS IR AND RX)
The receive amplifier transfers the receive signal from
input IR to output RX. The input impedance of the receive
amplifier, between pins IR and VEE, is 20 k. The voltage
gain from pin IR to RX is set at 33.4 dB. RX output is
intended to drive high ohmic (real) loads. Automatic gain
control is provided on the receive amplifier.
THE EARPIECE AMPLIFIER (PINS GAR AND QR)
The earpiece amplifier is an operational amplifier having
its output (QR) and inverting input (GAR) available. It can
be used in conjunction with two resistors to get some extra
gain or attenuation.
In an usual configuration (see Fig.8), output RX drives the
earpiece amplifier by means of RE1 connected between
RX and GAR. Feedback resistor RE2 of the earpiece
amplifier is connected between QR and GAR. Output QR
drives the earpiece.
The gain of the earpiece amplifier (from RX to QR) can be
set between +12 and 14 dB by means of resistor RE2.
The preferred value of RE1 is 100 k.
The earpiece amplifier offers a gain boost facility relative
to the initial gain. Resistor RE2 has to be replaced by the
network of RE21, RE22 and RE23 as shown in Fig.8.
The initial gain is defined by: R-----E---2---1R----+-E---1-R----E---2---2
which corresponds to RE23 = . The gain boost is realized
by a defined value of RE23 and is:
-R----E---2---1R----+-E---1-R----E---2---2
×
1
+
R-----E---2---1R-----E/--/-2---3R-----E---2--2- 
Two external capacitors CGAR (connected between GAR
and QR) and CGARS (connected between GAR and VEE)
ensure stability. The CGAR capacitor provides a first-order
low-pass filter. The cut-off frequency corresponds to the
time constant CGAR × RE2. The relationship
CGARS = 10 × CGAR must be fulfilled to ensure stability.
The output voltages of both amplifiers are specified for
continuous wave drive. The maximum output swing
depends on the DC line voltage VLN, the RCC resistor, the
ICC current consumption of the circuit, the IP current
consumption of the peripheral circuits and the load
impedance.
handbook, full pagewidth
Iline
Rline
RCC
ICC
CGAR
RE2
RE1
REXCH
TEA1114A LN
VCC QR
EARPIECE
AMPLIFIER
GAR
RX
VEXCH
0.5VCC
VEE
CGARS
CVCC
100 µF
RX
GAR
CGAR
QR
RE1
100 k
RE21
CGARS
10 µF
RE23
RE22
VEE
Addition for gain boost of
earpiece amplifier
MGK808
Fig.8 Earpiece amplifier configuration.
2000 Mar 21
9
 

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