clc451 National Semiconductor Corporation, clc451 Datasheet - Page 11

• Manufacturer Part Number: clc451
• Description: Single Supply, Low-power, High Output, Programmable Buffer
• Manufacturer: National Semiconductor Corporation

Twisted Pair Driver
The high output current and low distortion, of the
CLC451, make it well suited for driving transformers.
Figure 13 illustrates a typical twisted pair driver utilizing
the CLC451 and a transformer. The transformer
provides the signal and its inversion for the twisted pair.
To match the line’s characteristic impedance (Z
Where R
ance, (R
V
in
R
t
V
EE
R
R
L
L
m
3
1
2
4
eq
6.8 F
0.1 F
), and is approximated by:
+
= Z
= R
1k
CLC451
is the transformed value of the load imped-
Figure 13: Twisted Pair Driver
o
1k
eq
8
7
6
5
A
v
= 2
V = A
v
V
in
R
R
eq
m
1:n
V
V
-n
n
4
4
A V
A V
v in
v in
UTP
Z
o
V
o
o
) set:
1n
2
I
L
A V
R
v in
L
V
+
-
o
11
Select the transformer so that it loads the line with a
value close to Z
output impedance, R
frequency and can also affect the return loss. The return
loss, shown below, takes into account an ideal
transformer and the value of R
The load current (I
CLC451’s maximum output voltage and current by:
From the above current relationship, it is obvious that an
amplifier with high output drive capability is required.
Return Loss(dB)
o
, over the desired frequency range. The
L
) and voltage (V
20log
I
V
L
o
R
o
, of the CLC451 varies with
eq
10
I
n V
max
n
n
R
n
o
2
2
L
.
max
R
Z
o
o
o
) are related to the
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