clc5612 National Semiconductor Corporation, clc5612 Datasheet - Page 16

• Manufacturer Part Number: clc5612
• Description: Dual, High Output, Programmable Gain Buffer
• Manufacturer: National Semiconductor Corporation

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Application Division
Application Circuits
Single Supply Cable Driver
Figure 14 below shows the CLC5612 driving 10m of 75
coaxial cable. The CLC5612 is set for a gain of +2V/V to
compensate for the divide-by-two voltage drop at V
response after 10m of cable is illustrated in Figure 15 .
V
Differential Line Driver with Load
Impedance Conversion
The circuit shown in the Typical Application schematic on the
front page and in Figure 16 , operates as a differential line
driver. The transformer converts the load impedance to a
value that best matches the CLC5612’s output capabilities.
The single-ended input signal is converted to a differential
signal by the CLC5612. The line’s characteristic impedance
is matched at both the input and the output. The schematic
shows Unshielded Twisted Pair for the transmission line;
other types of lines can also be driven.
NOTE: Channel 2 not shown
75
o
Coaxial Cable
10m of 75
FIGURE 15. Response After 10m of Cable
FIGURE 14. Single Supply Cable Driver
V
in
= 10MHz, 0.5V
V
in
0.1 F
75
+5V
5k
5k
0.1 F
0.1 F
pp
20ns/div
2
3
1
4
(Continued)
1k
CLC5612
1k
+
1k
-
-
+
1k
8
7
6
5
DS015001-54
+5V
DS015001-53
o
6.8 F
0.1 F
. The
+
16
V
Set up the CLC5612 as a difference amplifier.
• Set the Channel 1 amplifier to a gain of +1V/V
• Set the Channel 2 amplifier to a gain of −1V/V
Make the best use of the CLC5612’s output drive capability
as follows:
where R
V
Output Current.
Match the line’s characteristic, impedance:
Select the transformer so that it loads the line with a value
very near Z
the CLC5612 also affects the match. With an ideal
transformer we obtain:
where Z
and |Z
The load voltage and current will fall in the ranges:
The CLC5612’s high output drive current an low distortion
make it a good choice for this application.
Return Loss
in
max
V
R
d/2
FIGURE 16. Differential Line Driver with Load
is the Output Voltage Range, and I
t
o
(
o
5612
eq
(
5612
3
1
2
4
is the transformed value of the load impedance,
o
)(j )|
over frequency range. The output impedance of
)(j ) is the output impedance of the CLC5612
1k
CLC5612
R
1k
Impedance Conversionn
1k
+
-
+
-
20 log
<<
m
I
V
o
1k
R
R
n
o
R
L
m
m
R
8
7
6
5
10
eq
I
max
Z
R
n
R
R
n V
R
R
R
-V
o
n
eq
R
m/2
m/2
t2
eq
L
2
eq
d/2
2 V
max
Z
I
1:n
max
o 5612
Z
Note: Supplies and bypassing not shown.
max
o
max
is the maximum
j
UTP
Z
o
,dB
DS015001-55
I
o
R
L