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Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement.

© Copyright June 1992 Gennum Corporation. All rights reserved. Printed in Canada.

DOCUMENT

IDENTIFICATION

PRODUCT PROPOSAL

This data has been compiled for market investigation purposes

only, and does not constitute an offer for sale.

ADVANCE INFORMATION NOTE

This product is in development phase and specifications are

subject to change without notice. Gennum reserves the right to

remove the product at any time. Listing the product does not

constitute an offer for sale.

PRELIMINARY DATA SHEET

The product is in a preproduction phase and specifications are

subject to change without notice.

DATA SHEET

The product is in production. Gennum reserves the right to make

changes at any time to improve reliability, function or design, in

order to provide the best product possible.

The above circuit represents a possible use of the GB4551 as

an input back-porch clamp for video mixers in a simple

Production Switcher.

For simplicity, the STROBE input is

derived from the GS4881 sync separator IC, driven from the

composite input signal.

of the GB4551. The value is usually between 15 and 47 ohms

depending on the total load capacitance seen by the device.

The GB4551 may be used anywhere in the circuit where

accurate DC restoration is required as shown by the second IC

following the output of the top GT4123.

COMPOSITE

VIDEO INPUT

COLOR BURST

FILTER

680k

10

NON-POLAR

470p

+10V

GB4551

4

2

6

5

3

7

1

8

COMPOSITE

VIDEO INPUT

VID B

VID A

CONTROL

OUT

0.1

6

4

8

5

2

STROBE

TO OTHER

GB4551s

BORDER

INPUT FROM

(GB4551)

OUT

VID B

VID A

CONTROL

BACKGROUND

VIDEO IN

(FROM GB4551)

KEY INPUT

VID B

VID A

CONTROL

INSERT

GB4551

STROBE

VIDEO

OUTPUT 1

VIDEO

OUTPUT 2

BACK

PORCH

PULSE

5V

0V

3

5

1

7

3

5

1

7

3

5

1

7

GT4123

GT4123

GT4123

+5V

0.1

0.1

0.1

0.1

GS4881

SYNC. SEP.

APPLICATION CIRCUIT

Fig. 7 GB4551 Driving Several GT4123 Video Mixers

All resistors in ohms, all capacitors

in microfarads unless otherwise stated.