clc450 National Semiconductor Corporation, clc450 Datasheet - Page 10

• Manufacturer Part Number: clc450
• Description: Single Supply, Low-power, High Output, Current Feedback Amplifier
• Manufacturer: National Semiconductor Corporation

Components not used:
The evaluation boards are designed to accommodate
dual supplies. The boards can be modified to provide
single supply operation. For best performance; 1) do
not connect the unused supply, 2) ground the unused
supply pin.
SPICE Models
SPICE models provide a means to evaluate amplifier
designs. Free SPICE models are available for National’s
monolithic amplifiers that:
The readme file that accompanies the diskette lists
released models, and provides a list of modeled parame-
ters. The application note OA-18, Simulation SPICE
Models for National’s Op Amps, contains schematics and
a reproduction of the readme file.
Single Supply Cable Driver
The typical application shown on the front page shows
the CLC450 driving 10m of 75
CLC450 is set for a gain of +2V/V to compensate for the
divide-by-two voltage drop at V
Single Supply Lowpass Filter
Figures 9 and 10 illustrate a lowpass filter and design
equations. The circuit operates from a single supply of
+5V. The voltage divider biases the non-inverting input to
2.5V. And the input is AC coupled to prevent the need for
level shifting the input signal at the source. Use the
design equations to determine R
on the desired Q and corner frequency.
http://www.national.com
V
in
0.1 F
R
tions (Select R
= R
C
C
C
R
Support Berkeley SPICE 2G and its many derivatives
Reproduce typical DC, AC, Transient, and Noise
performance
Support room temperature simulations
t
1
3
5
1
, C
, C
, C
- Optional resistor for inverting gain configura-
Figure 9: Lowpass Filter Topology
thru R
g
5k
158
5k
Application Circuits
|| R
2
4
6
R
, C
- 0.1 F ceramic capacitors
- 6.8 F tantalum capacitors
1
t
)
7
8
, C
158
100pF
R
1.698k
8
2
C
t
2
to yield desired input impedance
R
0.1 F
3
2
g
o
.
CLC450
+
-
1
+5V
, R
7
4
coaxial cable. The
2
, C
0.1 F
1k
C
R
1
1
f
6
, and C
0.1 F
2
based
100
V
o
10
V
This example illustrates a lowpass filter with Q = 0.707
and corner frequency f
sen to achieve a maximally flat, Butterworth response.
Figure 11 indicates the filter response.
Twisted Pair Driver
The high output current and low distortion, of the
CLC450, make it well suited for driving transformers.
Figure 12 illustrates a typical twisted pair driver utilizing
the CLC450 and a transformer. The transformer
provides the signal and its inversion for the twisted pair.
To match the line’s characteristic impedance (Z
in
R
t
R
g
3
2
R
R
CLC450
+
Gain K 1
Corner frequency
Q
For R
Q
-
L
m
c
-15
-21
= Z
-3
-9
A
= R
3
R
(3 K)
v
Figure 11: Lowpass Response
Figure 12: Twisted Pair Driver
f
RC
Figure 10: Design Equations
V = A
1
R C
o
R C
1
1
1
6
eq
2 2
1 1
R
R
R
v
1M
g
f
2
V
in
R
R
R
eq
R
R and C
c
m
g
Frequency (Hz)
f
= 10MHz. A Q of 0.707 was cho-
R C
R C
1 2
2 1
I:n
10M
c
1
1
V
V
R R C C
C
(1 K)
-n
1 2 1 2
n
4
2
4
100M
A V
A V
v in
1
v in
C
UTP
Z
o
R C
R C
V
2 2
1 1
o
o
1n
2
) set:
I
L
A V
R
v in
L
V
+
-
o