GT4124 Video Multiplier
with Strobed DC Restore
DATA SHEET
FEATURES
•
broadcast quality video multiplier with a very accurate
back porch clamp, (less than 2mV DC offset)
•
30 MHz at -1.0dB video and control channel bandwidth
•
one external frequency compensation adjustment
•
ultra low differential gain and differential phase,
(typically 0.01% and 0.01 deg.)
•
adjustable DC offset and span on the control input
•
adjustable clamp reference level
•
active low STROBE input
•
20 pin PDIP and SOIC packaging.
APPLICATIONS
•
Production switcher video mixers
•
Linear Keyers
ORDERING INFORMATION
Part Number
GT4124-CDF
GT4124-CKF
Package Type Temperature Range
20 pin PDIP
20 pin SOIC
0 to 70˚
0 to 70˚
An application note entitled "Using the GT4122 and GT4124
Video Mixer ICs" (Document 520-44) is available from
Gennum Corporation.
DESCRIPTION
The GT4124 multiplier is a monolithic dual-channel video
multiplier for use in the professional broadcast field. It
incorporates a very fast and accurate strobed clamp to
insure black level accuracy.
Featuring two wideband video inputs and a single control
input, the GT4124 achieves high quality video mixing of
the two synchronized video input signals to a single output
by implementing the transfer function:
V
OUT
= V
IN
• V
A
C
+ V
IN
(1 - V )
B
C
where V
C
is the control input voltage, which may be varied
over the control range, and V
IN
and V
IN
are the video
A
B
input signals.
The GT4124 operates with power supply voltages of
±
9 to
±
12 volts. At a nominal supply of
±
10 volts, it draws an
average of 20 mA of current. The GT4124 is available in
20 pin PDIP and 20 pin SOIC packages.
PIN DESIGNATION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
+V
S
C
HOLD
COMP
C
OS1
C
OS2
S1
V
REF
S2
V
CONT
GND
STROBE
R
EXT
+IN A
-IN A
positvive supply voltage
clamp holding capacitor
output freq'y comp'n R-C
control input offset adjust
control input offset adjust
span adjust
0.5 volt reference input
span adjust
control signal input
ground
strobe input
current setting resistor
A video + signal input
A video - signal input
-
V
S
+
V
S
GND
V
NOM
0.5V
C
HOLD
+
IN A
-
IN A
+
AMP 1
STROBE
XA
CLAMP
CLAMP REF.
CLAMP SIG.
-
VIDEO
INPUT A
+
IN B
-
IN B
+
AMP 2
+
V
CA
=0.5 + V
K
+
+
Σ4
AMP 4
COMP.
OUTPUT
Σ1
+
XB
R
EXT
BIAS
-
VIDEO
INPUT B
V
CB
=0.5 - V
K
+
Σ2
Σ3
+
-
V
K
AMP 3
V
K
A
K
+
CONTROL
VOLTAGE
(VCONT)
S1
S2
C
OS2
C
OS1
-
+
V
REF
+
+
0.5V
+
-
-
V
NOM
CLAMP SIG clamp signal
CLAMP REF clamp reference
+IN B
-IN B
OUTPUT
-V
S
B video + signal input
B video - signal input
video output
negative supply voltage
Device Function: V
OUT
= A
OL
[V
A
(0.5+V
K
) + V
B
(0.5 - V
K
)] where A
OL
~ 2000, V
K
=V
CONT
- V
REF,
AK
≈
0.85 R
EXT
R
SPAN
FUNCTIONAL BLOCK DIAGRAM
Document No. 520 - 59 - 2
Revision Date: February 1994
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. (905) 632-2996 fax: (905) 632-5946
Japan Branch: A-302 Miyamae Village, 2-10-42 Miyamae, Suginami-ku, Tokyo 168, Japan
tel. (03) 3334-7700
fax: (03) 3247-8839
GENNUM [ GENNUM CORPORATION ]
