PIN DESIGNATION

1+V

S

positvive supply voltage

2C

HOLD

clamp holding capacitor

3

COMP

output freq'y comp'n R-C

4C

OS1

control input offset adjust

5C

OS2

control input offset adjust

6

S1

span adjust

7V

REF

0.5 volt reference input

8

S2

span adjust

9V

CONT

control signal input

10

GND

ground

11

STROBE

strobe input

12

R

EXT

current setting resistor

13

+IN A

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

Document No. 520 - 59 - 2

DATA SHEET

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

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

GT4124 Video Multiplier

with Strobed DC Restore

FUNCTIONAL BLOCK DIAGRAM

CONTROL

VOLTAGE

(VCONT)

+

-

GND

BIAS

AMP 3

COMP.

OUTPUT

AMP 1

AMP 2

+

-

+

-

XA

XB

+

+

AMP 4

-

+

S1

S2

0.5V

Σ2

Σ3

+

-

+

-

+

+

Σ4

+

+

STROBE

CLAMP REF.

CLAMP SIG.

Σ1

CLAMP

+

+

VIDEO

INPUT A

VIDEO

INPUT B

0.5V

ORDERING INFORMATION

Part Number

Package Type Temperature Range

GT4124-CDF

20 pin PDIP

0 to 70˚

GT4124-CKF

20 pin SOIC

0 to 70˚

Revision Date: February 1994

A

B

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

C

+ V

IN

(1 - V

C

)

where V

C

is the control input voltage, which may be varied

A

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.