LT1399 Linear Technology Corporation, LT1399 Datasheet - Page 16

• Manufacturer Part Number: LT1399
• Description: Low Cost Dual And Triple 300mhz Current Feedback Amplifiers With Shutdown
• Manufacturer: Linear Technology Corporation

LT1398/LT1399/LT1399HV
TYPICAL
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 . The gain resistor is created
from the parallel combination of R6 and R7, giving a
Thevenin equivalent 80.4
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
RELATED PARTS
16
PART NUMBER
LT1203/LT1205
LT1204
LT1227
LT1252/LT1253/LT1254
LT1259/LT1260
LT1395/LT1396/LT1397
LT1675/LT1675-1
LT1806/LT1807
LT1809/LT1810
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] FAX: [phone] www.linear-tech.com
A
PPLICATI
SOURCE
VIDEO
DESCRIPTION
150MHz Video Multiplexers
4-Input Video MUX with Current Feedback Amplifier
140MHz Current Feedback Amplifier
Low Cost Video Amplifiers
Dual/Triple Current Feedback Amplifier
Single/Dual/Quad Current Feedback Amplifiers
Triple/Single 2:1 Buffered Video Mulitplexer
Single/Dual 325MHz Rail-to-Rail In/Out Op Amp
Single/Dual 180MHz Rail-to-Rail In/Out Op Amp
75
connected to 3.75V. This
O
Figure 10. Single Supply RGB Video Amplifier (1 of 3 Channels)
U
V
IN
R1
1000
R2
1300
R3
160
R4
75
R5
2.32
5V
R6
107
R7
324
input. Assuming a 75 source impedance for the signal
driving V
A1’s positive input is 3V + 0.4V
ance of 714 . The combination of these two inputs gives
an output at the cathode of D2 of 2 • V
DC offset. The 75 back termination resistor R9 halves
the signal again such that V
of V
It is important to note that the 4.7 F 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.
IN
COMMENTS
2:1 and Dual 2:1 MUXs with 25ns Switch Time
1100V/ s Slew Rate, Shutdown Mode
Single, Dual and Quad Current Feedback Amplifiers
130MHz Bandwidth, 0.1dB Flatness >30MHz
400MHz Bandwidth, 0.1dB Flatness >100MHz
350V/ s, Low Distortion
Cascadable Enable 64:1 Multiplexing
2.5ns Switching Time, 250MHz Bandwidth
Low Distortion, Low Noise
+
–
1/3 LT1399
.
6V TO 12V
A1
V
IN
S
, the Thevenin equivalent signal arriving at
324
R8
1N4148
D1
4.7 F
C1
1N4148
1398/99 F10
D2
OUT
LINEAR TECHNOLOGY CORPORATION 1998
75
LT/TP 0501 2K REV A • PRINTED IN USA
equals a buffered version
R9
IN
, with a source imped-
V
OUT
IN
with no additional
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