LM1202 datasheet(13/18 Pages) NSC

13 / 18 page

Applications of the LM1202

SINGLE VIDEO CHANNEL

A typical application for a single video channel is shown in

Figure 9 The video signal is AC coupled to pin 6 The

LM1202 internally biases the video signal to 26 VDC Con-

trast control is achieved by applying a 0V to 4V DC voltage

at pin 8 The amplifier’s gain is minimum (ie maximum sig-

nal attenuation) if pin 8 is at 0V and is maximum if pin 8 is at

4V With pin 9 (drive control) at 0V the amplifier has a maxi-

mum gain of 10

For DC restoration a clamp signal must be applied to the

clamp gate input (pin 14) The clamp signal should be logic

low (less than 08V) only during the back porch (black level

reference period) interval (see

Figure 2 ) The clamp gate

input is TTL compatible Brightness control is provided by

applying a 0V to 4V DC voltage at pin 19 For example if pin

19 is biased at 1V then the video signal’s black level will be

clamped at 1V A 510X load resistor is connected from the

video output pin (pin 17) to ground This resistor biases the

output stage of the amplifier For power dissipation consid-

erations the load resistor should not be much less than

510X

RGB VIDEO PREAMPLIFIER

Figure 10 shows an RGB video preamplifier circuit using

three LM1202s Note that pins 1 and 2 of IC1 are connected

to pins 1 and 2 of IC2 and IC3 respectively This allows IC1

to provide a master contrast control and optimum contrast

tracking Adjusting the contrast voltage at pin 8 of IC1 will

vary the gain of all three video channels Drive control input

(pin 9) of each LM1202 allows individual gain adjustment for

achieving white balance

The black level of each video channel can be individually

adjusted to the desired voltage by adjusting the voltage at

pin 19 In a DC-coupled cathode drive application adjusting

the voltage at pin 19 of each IC will provide cutoff adjust-

ment In an AC-coupled cathode drive application the video

signal is AC coupled and DC restored at the cathode In

such an application the video signal’s black level may be

clamped to the desired level by simply biasing pin 19 to the

black level voltage by using a voltage divider at pin 19

http

www nationalcom

LM1202 Datasheet(PDF) 13 Page - National Semiconductor (TI)

LM1202 Datasheet(HTML) 13 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Datasheet Download

Link URL