tea1114auh NXP Semiconductors, tea1114auh Datasheet - Page 9

• Manufacturer Part Number: tea1114auh
• Description: Low Voltage Telephone Transmission Circuit With Dialler Interface And Regulated Strong Supply
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Receiving stage (pins IR, RX, GAR and QR)
The receive part consists of a receive amplifier and an
earpiece amplifier.
T
The receive amplifier transfers the receive signal from
input IR to output RX. The input impedance of the receive
amplifier, between pins IR and V
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.
T
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 R
RX and GAR. Feedback resistor R
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 R
2000 Mar 21
handbook, full pagewidth
HE RECEIVE AMPLIFIER
HE EARPIECE AMPLIFIER
Low voltage telephone transmission circuit with
dialler interface and regulated strong supply
V EXCH
R EXCH
I line
TEA1114A
R line
(
PINS
(
PINS
IR
GAR
AND
EE
E1
LN
E2
, is 20 k . The voltage
AND
connected between
RX)
of the earpiece
AMPLIFIER
EARPIECE
R CC
QR)
Fig.8 Earpiece amplifier configuration.
I CC
V CC
V EE
E2
0.5V CC
.
QR
C GAR
9
R E2
The preferred value of R
The earpiece amplifier offers a gain boost facility relative
to the initial gain. Resistor R
network of R
The initial gain is defined by:
which corresponds to R
by a defined value of R
Two external capacitors C
and QR) and C
ensure stability. The C
low-pass filter. The cut-off frequency corresponds to the
time constant C
C
The output voltages of both amplifiers are specified for
continuous wave drive. The maximum output swing
depends on the DC line voltage V
I
consumption of the peripheral circuits and the load
impedance.
–
CC
R
------------------------------ -
GARS
E21
current consumption of the circuit, the I
GAR
R
R E1
+
= 10
E1
RX
R
E22
E21
C
GARS
, R
GAR
GAR
1
E22
+
must be fulfilled to ensure stability.
100 F
R
--------------------------------- -
(connected between GAR and V
C VCC
R
and R
E21
GAR
GAR
E23
E23
E2
QR
RX
C GAR
E1
R
. The relationship
Addition for gain boost of
earpiece amplifier
GAR
// R
E23
capacitor provides a first-order
and is:
C GARS
= . The gain boost is realized
is 100 k .
E2
E23
–
E22
(connected between GAR
R
------------------------------ -
has to be replaced by the
as shown in Fig.8.
E21
LN
R
R E1
100 k
R E21
R E22
, the R
10 F
+
E1
Product specification
R
TEA1114A
E22
R E23
CC
P
current
C GARS
resistor, the
MGK808
V EE
EE
)