16
LT1398/LT1399/LT1399HV
sn13989 13989fas
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
LT1395/LT1396/LT1397 Single/Dual/Quad Current Feedback Amplifiers 400MHz Bandwidth, 0.1dB Flatness >100MHz
LT1675/LT1675-1 Triple/Single 2:1 Buffered Video Mulitplexer 2.5ns Switching Time, 250MHz Bandwidth
LT1806/LT1807 Single/Dual 325MHz Rail-to-Rail In/Out Op Amp Low Distortion, Low Noise
LT1809/LT1810 Single/Dual 180MHz Rail-to-Rail In/Out Op Amp 350V/µs, Low Distortion
LINEAR TECHNOLOGY CORPORATION 1998
LT/TP 0501 2K REV A • PRINTED IN USA
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear-tech.com
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 324Ω. The gain resistor is created
from the parallel combination of R6 and R7, giving a
Thevenin equivalent 80.4Ω 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 75Ω source impedance for the signal
driving V
IN
, the Thevenin equivalent signal arriving at
A1’s positive input is 3V + 0.4V
IN
, with a source imped-
ance of 714Ω. The combination of these two inputs gives
an output at the cathode of D2 of 2 • V
IN
with no additional
DC offset. The 75Ω back termination resistor R9 halves
the signal again such that V
OUT
equals a buffered version
of V
IN
.
It is important to note that the 4.7µF 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
4.7µF
D2
1N4148
R9
75Ω
R8
324Ω
V
S
6V TO 12V
R7
324Ω
R5
2.32Ω
R4
75Ω
V
IN
R2
1300Ω
R1
1000Ω
5V
R6
107Ω
R3
160Ω
V
OUT
1398/99 F10
VIDEO
SOURCE
75Ω
Figure 10. Single Supply RGB Video Amplifier (1 of 3 Channels)
