Datasheet

18
LT1204
U
SA
O
PP
L
IC
AT
ITY
P
I
CA
L
CABLE
OUTPUT
LT1204
#2 OUTPUT
A0 PIN 9
1204 TA05
Differential Receiver Switching Waveforms
FREQUENCY (Hz)
–60
DIFFERENTIAL RECEIVER RESPONSE (dB)
–40
–20
0
20
10k 1M 10M 100M
1204 TA06
100k
V
S
= ±15V
R
L
= 100Ω
DIFFERENTIAL MODE RESPONSE
COMMON MODE RESPONSE
4-Input Twisted-Pair Driver
It is possible to send and receive color composite video
signals appreciable distances on a low cost twisted pair.
The cost advantage of this technique is significant. Stan-
dard 75Ω RG-59/U coaxial cable cost between 25¢ and
50¢ per foot. PVC twisted pair is only pennies per foot.
Differential signal transmission resists noise because the
interference is present as a common mode signal. The
LT1204 can select one of four video cameras for instance,
and drive the video signal on to the twisted pair. The circuit
uses an LT1227 current feedback amplifier connected with
a gain of –2, and an LT1204 with a gain of 2. The 47Ω
resistors back-terminate the low cost cable in its charac-
teristic impedance to prevent reflections. The receiver for
the differential signal is an LT1193 connected for a gain of
2. Resistors R1, R2 and capacitors C1, C2 are used for
cable compensation for loss through the twisted pair.
Alternately, a pair of LT1204s can be used to perform the
differential to single-ended conversion.
Multiburst Pattern Passed Through 1000 Feet of Twisted Pair,
No Cable Compensation
Multiburst Pattern Passed Through 1000 Feet of Twisted Pair,
with Cable Compensation
1204 TA08
OUTPUT
INPUT
INPUT
OUTPUT
1204 TA09
Differential Receiver Response