The RF input signal reaches a symmetrically built up mixer, its input stages in common base enable very well
large - signal characteristics. With exception of the RF input signal the mixer receives via buffer stages an ultra
pure oscillator signal with sufficient amplitude, generated by the oscillator itself. Moreover, the oscillator signal is
available at pin 9 via buffer stages for instance in order to drive frequency - synthesizers. The IF signal, supplied
from the mixer, can be amplified by a linear IF preamplifier which is proofed against overdriving in order to
balance signal attenuation by selection means. Wideband or narrow band or also combined gain control of the
pre stage can be selected by means of an internal generated control voltage.
Further on the TDA1574 contains an electronic standby switch. The oscillator can be blocked by this switch and
the gain of the RF pre stage can be reduced, so that the IC is ready at once after activating of the FM operation,
without thermal transients.
An integrated voltage supply delivers a temperature independent voltage of about 4.15 V to provide the oscillator
and to generate an internal comparison voltage. This voltage is available at pin 5.
Absolute Maximum Ratings
min
Supply voltage
Mixer output DC voltage
V
CC
V
16-4
V
17-4
V
12-4
0.3
0.3
max
18
35
35
7
unit
V
V
V
V
Narrow band information
input voltage
Reference voltage
Standby switch input voltage
Total power dissipation
Ambient operating temperature
Storage temperature
Thermal resistance
V
5-4
V
11-4
P
tot
T
a
T
s
R
th
0.3
0.3
7
23
800
V
V
mW
°C
°C
K/W
-40
-55
85
150
80
note: All pins are short-circuit protected to ground
Recommended Operational Conditions
min
Supply voltage
Ambient operating temperature
V
9
T
a
7.0
-40
max
16
85
unit
V
°C
09/00
TDA1574
3
GSG [ GUNTER SENICONDUCTOR GMBH. ]
