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參數資料
| 型號： | GT4124-CDF |
| 英文描述： | Analog Multiplier |
| 中文描述： | 模擬乘法器 |
| 文件頁數： | 1/15頁 |
| 文件大小： | 387K |
| 代理商： | GT4124-CDF |
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R
EXT
V
REF
V
C
+
-
V
S
GND
+
IN A
-
IN A
-
IN B
V
CA
=0.5 + V
K
+
IN B
+
V
S
BIAS
AMP 3
-
+
COMP
OUT
V
NOM
AMP 1
AMP 2
+
XA
V
CB
=0.5 - V
K
XB
+
+
AMP 4
A
K
C
OS1
C
OS2
S1
S 2
0.5V
Σ2
Σ3
+
-
+
-
+
+
V
K
-
V
K
Σ4
+
+
STROBE
C
HOLD
CL
REF
CL
SIG
Σ1
CLAMP
V
NOM
+
+
R
EXT
C
OS1
V
REF
C
OS2
V
C
+
-
V
S
GND
A
OS2
+
IN A
-
IN A
B
OS2
-
IN B
V
CA
=0.5 + V
K
+
IN B
+
V
S
B
OS1
A
OS1
BIAS
AMP 3
-
+
S1
S 2
COMP
OUT
V
NOM
AMP 1
AMP 2
+
XA
V
CB
=0.5 - V
K
XB
+
+
AMP 4
A
K
0.5V
Σ2
Σ3
+
-
+
-
+
+
V
K
-
V
K
+
+
Σ1
V
NOM
For both devices, the input signals are applied to conventional
differential amplifiers (AMP1 and AMP2). In the case of the
GT4122, each amplifier has provisions for individually adjusting
the DC offset (OFFSET). For the GT4124, these offsets are
trimmed by on-chip resistors.
Following each input amplifier, the signals are applied to
linear multiplier circuits (XA and XB) whose outputs are the
product of the incoming signals and controlling voltages (V
CA
)
or (V
CB
). The controlling voltage V
CA
is the sum of a nominal
0.5V source (V
NOM
) and a variable source V
K
while V
CB
is
made up of the sum of the nominal voltage V
NOM
and -V
K
.
V
and -V
are themselves proportional to the difference
between an externally applied reference voltage (V
) and
an externally applied CONTROL voltage (V
). The voltages V
K
and -V
are produced by a differential amplifier (AMP3) whose
gain is A
. This gain can be altered by two external resistors,
R
EXT
and R
SPAN
according to the following formula:
Note that R
EXT
is connected between the R
EXT
pin and ground
and R
SPAN
is connected between the pins S1 and S2.
Each of the voltages (+V
K
and -V
K
) is applied to summing
circuits (
Σ
2 and
Σ
3) whose second inputs are DC voltage
sources that can also be slightly varied. The nominal value of
these voltage sources is 0.5 volts. When they are exactly 0.5V
and when V
C
= V
REF
then the gain of each signal channel of
the mixer is 0.5 (50%).
By connecting the ends of an external potentiometer
(CONTROL OFFSET) between the offset pins COS1 and COS2,
the voltage sources can be altered differentially. If a second
potentiometer (50% GAIN) is connected between the wiper of
the CONTROL OFFSET potentiometer and the supply voltage,
the voltage sources can be varied in a common mode fashion.
In this way not only can the control range of the mixer be
varied but also the point at which 50% of each input signal
appears at the output.
The outputs from the multiplier circuits (XA and XB) are then
applied to a summing circuit (
Σ
1) whose output feeds a
wideband amplifier (AMP4) and presents the mixed signals to
the outside world.
Although there are two separate differential inputs, the usual
operational amplifier gain-setting methods can be applied to
determine the closed loop gain of the mixer. Usually the mixer
Fig. 2 Functional Block Diagram of the GT4124
Fig. 1 Functional Block Diagram of the GT4122
0.85 R
A
≈
————— [1k
< R
EXT
< 3k
]
R
SPAN
APPLICATION NOTE
by Ian Ridpath, Senior Applications Engineer, Video & Broadcast Group
INTRODUCTION and DEVICE TOPOLOGY
The GT4122 and GT4124 are broadcast quality monolithic
integrated circuits specifically designed to linearly mix two
video signals under the control of a third channel.
Figures 1 and 2 show the functional block diagrams of the
GT4122 and the GT4124 respectively. The corresponding
external connections are shown in Figures 3 and 6.
Using the GT4122 & GT4124
Video Mixer ICs
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|---|---|
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|---|---|
| GT4124-CKF | 制造商:GENNUM 制造商全稱:GENNUM 功能描述:GT4124 Video Multiplier with Strobed DC Restore |
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| GT422 | 制造商:Cornell Dubilier Electronics 功能描述:Cap Ceramic 22pF 3000V SL 5% (10 X 6mm) Radial 9.5mm 85°C |
| GT424 | 制造商:Cornell Dubilier Electronics 功能描述:Cap Ceramic 24pF 3000V SL 5% (10 X 6mm) Radial 9.5mm 85°C |
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