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LT1398/LT1399/LT1399HV

©LINEAR TECHNOLOGY CORPORATION 1998

13989f LT/TP 0699 4K • PRINTED IN USA

APPLICATI

TYPICAL

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

PART NUMBER

DESCRIPTION

COMMENTS

LT1203/LT1205

150MHz Video Multiplexers

2:1 and Dual 2:1 MUXs with 25ns Switch Time

LT1204

4-Input Video MUX with Current Feedback Amplifier

Cascadable Enable 64:1 Multiplexing

LT1227

140MHz Current Feedback Amplifier

1100V/

µs Slew Rate, Shutdown Mode

LT1252/LT1253/LT1254

Low Cost Video Amplifiers

Single, Dual and Quad Current Feedback Amplifiers

LT1259/LT1260

Dual/Triple Current Feedback Amplifier

130MHz Bandwidth, 0.1dB Flatness > 30MHz

LT1675

Triple 2:1 Buffered Video Mulitplexer

2.5ns Switching Time, 250MHz Bandwidth

RELATED PARTS

Single Supply RGB Video Amplifier

The LT1399 can be used with a single supply voltage of

6V or more to drive ground-referenced RGB video. In

Figure 10, two 1N4148 diodes D1 and D2 have been

placed in series with the output of the LT1399 amplifier

A1 but within the feedback loop formed by resistor R8.

These diodes effectively level-shift A1’s output down-

ward by 2 diodes, allowing the circuit output to swing to

ground.

Amplifier A1 is used in a positive gain configuration. The

feedback resistor R8 is 324

Ω.Thegainresistoriscreated

from the parallel combination of R6 and R7, giving a

Thevenin equivalent 80.4

Ω connected to 3.75V. This

gives an AC gain of + 5 from the noninverting input of

amplifier A1 to the cathode of D2. However, the video

input is also attenuated before arriving at A1’s positive

input. Assuming a 75

Ω source impedance for the signal

ance of 714

Ω. The combination of these two inputs gives

DC offset. The 75

Ω back termination resistor R9 halves

It is important to note that the 4.7

µF capacitor C1 has

been added to provide enough current to maintain the

voltage drop across diodes D1 and D2 when the circuit

output drops low enough that the diodes might otherwise

reverse bias. This means that this circuit works fine for

continuous video input, but will require that C1 charge up

after a period of inactivity at the input.

–

+

A1

1/3 LT1399

D1

1N4148

C1

4.7

µF

D2

1N4148

R9

75

Ω

R8

324

Ω

6V TO 12V

R7

324

Ω

R5

2.32

Ω

R4

75

Ω

R2

1300

Ω

R1

1000

Ω

5V

R6

107

Ω

R3

160

Ω

1398/99 F10

Figure 10. Single Supply RGB Video Amplifier (1 of 3 Channels)