TBA120S
^ft
W
PLESSEY
Semiconductors
TBA120S
LIMITING IF AMPUFIER/FM DETECTOR
The TBA120S is a symmetrical 8-stage limiting amplifier
with a symmetrical coincidence demodulator and remote
DC volume control. The circuit is especially suited for the EARTH[ Oi u ] INPUT
sound IF section of TV receivers and for FM/IF l/P BIAS[ J u ]FEEDBACK BIAS
amplification/demodulation in FM radio receivers.
FREE COLLECTOR [ ] ZENER 0/P
An auxiliary circuit, consisting of a transistor with free ' TBA "
FREE BASE[ < 120S « ] + VE SUPPLY
base and collector and a 12V Zener diode, is also
VOLUME CONTROL[1 19 ] LIM. AMP 0/P2
incorporated on the chip. The transistor can be used as an
LIM. AMP. 0/P 11[ » ]TUNEO CCT
AF preamplifier 0c<5mA) or as a bass/treble switch using
voltage-controlled on/off switching of an R-C circuit. TUNEO CCT[ ] AUOtO 0/P
The Zener diode can be used to stabilize the chip supply
voltage or that of other circuits in the system dz<15mA). DPI 4 QP14
The TBA120S is supplied in two group variants, with Fig. 1 Pin connections
volume as the parameter. A decrease in volume of 30 dB
requires a resistor between pin 5 and earth with a value
depending on the group number as shown in the following
table. The group number is printed on the package.
FEATURES
• Outstanding Limiting Qualities
• High A M Suppression
Group III IV • Wide Supply Voltage Range
• Low External Component Count
R s (ktt) 2.1 — 2.5 2.4-2.9
APPLICATIONS
T V Sound Systems
FM Radio Receivers
i q r r p FM Tuners
ELECTRONIC
AMP
DEMODULATOR
ATTENUATOR QUICK REFERENCE D A T A
IS Supply Voltage: + 1 2 V (Typ.)
Operating Frequency : Up to 12MHz
a Current Consumption: 14mA (Typ.)
IF Voltage Gain: 68dB (Typ.)
A F Output Voltage: 1.1V r.m.s. (Typ.)
V o l u m e Control Range: 70dB (Typ.)
Second Source Availability
Fig.! TBA120S block diagram
133
TBA120S
ELECTRICAL CHARACTERISTICS
Test Conditions (unless otherwise stated):
V C C = +12V
T A = +25°C
f = 5.5MHz
Af = ±50kHz
f
mod " ' k H z
Value
Characteristics Symbol Units Conditions
Min. Typ. Max.
Amplifier/demodulator
Frequency range f 0 12 MHz
IF voltage gain V 6 / V , 4 GV 68 dB
IF output voltage Vopp 250 mV Limiting each output
AF output voltage Vaf 1.1 V r.m.s. V,=10mV, Q=45, K=4%
0.55 V r.m.s. Vi=10mV,Q=20, K=1%
Input voltage at start of limiting V,im 30 60 A>V 0=45
Input impedance Z; 15/6 40/4.5 kfi/pF
Output resistance (pin 8) Ro 2.6 kfi
Volume control range V a f max 70 dB
V a f min
DC component of o/p signal v8 7.3 V vro
AM suppression 3AM 45 55 dB Vi=50Q(iV, m=30%
Potentionmeter resistance R
5
—IdB down 3.7 4.7 kfi
—70dB down 1.0 1.4 kfi
v
Control voltage 5
—1dB down 2.4 2.6 V
—70dB down 1.3 V
Total current requirement Ice 10 14 18 mA R5 = -
12 16 20 mA R5 = O
Auxiliary circuit
Zener voltage V12. 12.5 13.5 14.5 V 1 ) 2 = 5mA
Zener resistance Rz 30 n
Transistor breakdown voltage BVceo 13 V U=0, 13=50
Current gain hFE 30 l 3 =1mA
ABSOLUTE MAXIMUM RATINGS Zener current, 112
Continuous: 15mA
Max. 1 min: 20mA
Supply voltage VcC- 18V Volume control voltage, V 5 : 4V
Operating temperature —10°Cto +70° C Collector current, (3: 5mA
Storage temperature - 2 5 ° C to +125°C Current l 4 : 2mA
Total power dissipation, P t o t Shunt resistance R 1 3 / 1 4 : <1kJ2
Continous: 400mW
Max. 1 min: 500mW
134
TBA120S
/
/
>
J
/
f
/
/
//
/
I
5 12
V, . O
t mV
1 • 5-5 MHl
/
J
/
/
/
CONTROL VOLTAGE V 5 (V) R5 (k«>
Fig. 3 Volume control voltage characteristic Fig. 4 Volume control resistance characteristic
\\ vcc 12V
V Af s' 50k Hx
\ I I
kt :l.5r>F
S
2 \ —ks 91. /2 2k
\
kt V.C =MO»l/ttkA
-To -to -50 -10 J' O -10 .10 o
AUDIO OUTPUT LEVEL VAF RELATIVE
TOMAX 0/rtdB)
Fig. S Audio output r. supply voltage
Fig. 6 Distortion factor (kl as a function of audio output voltage
VAF
135
TBA120S
Fig. 7 AM suppression characteristics
136
