GT4124 Datasheet, PDF (1/5 Pages) Gennum Corporation – GT4124 Video Multiplier with Strobed DC Restore

GT4124 Video Multiplier
with Strobed DC Restore
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 Package Type Temperature Range
GT4124-CDF 20 pin PDIP
0 to 70˚
GT4124-CKF 20 pin SOIC
0 to 70˚
DATA SHEET
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
•
A
V_C
+
V_IN
(1
B
-
V_C)
where V_C is the control input voltage, which may be varied
over the control range, and VIN_A and VIN_B are the video
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.
An application note entitled "Using the GT4122 and GT4124
Video Mixer ICs" (Document 520-44) is available from
Gennum Corporation.
PIN DESIGNATION
1 +V_S
2 C_HOLD
3 COMP
positvive supply voltage
clamp holding capacitor
output freq'y comp'n R-C
4 C_OS1
5 C_OS2
6 S1
control input offset adjust
control input offset adjust
span adjust
7 V_REF
8 S2
0.5 volt reference input
span adjust
9 V_CONT
10 GND
control signal input
ground
11 STROBE strobe input
12 R_EXT
13 +IN A
current setting resistor
A video + signal input
14 -IN A
A video - signal input
15 CLAMP SIG clamp signal
16 CLAMP REF clamp reference
17 +IN B
B video + signal input
18 -IN B
B video - signal input
19 OUTPUT video output
20 -V_S
negative supply voltage
+IN A
- IN A
+
AMP 1
-
VIDEO
INPUT A
+IN B
- IN B
+
AMP 2
-
VIDEO
INPUT B
XA
V_CA=0.5 + V_K
XB
+
+
Σ1 ₊ Σ4
+
V_CB=0.5 - V_K
CLAMP
AMP 4
BIAS
C_HOLD
STROBE
CLAMP REF.
CLAMP SIG.
COMP.
OUTPUT
REXT
- VS
+VS
GND
V_NOM
+ _{Σ2 + - VK}
Σ3 ⁺
V_K
+
0.5V
+
-
0.5V
+
V_NOM
-
AMP 3
-
AK
+
VREF
CONTROL
VOLTAGE
(VCONT)
S1
S2
COS2
COS1
Device Function: VOUT = AOL [VA (0.5+VK) + VB(0.5 - VK)] where AOL ~ 2000, VK=VCONT - VREF, AK ≈ 0.85 REXT
RSPAN
FUNCTIONAL BLOCK DIAGRAM
Revision Date: February 1994
Document No. 520 - 59 - 2
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. [phone] fax: [phone]
Japan Branch: A-302 Miyamae Village, 2-10-42 Miyamae, Suginami-ku, Tokyo 168, Japan tel. [phone] fax: [phone]