clc411 National Semiconductor Corporation, clc411 Datasheet - Page 4

• Manufacturer Part Number: clc411
• Description: High-speed Video Op Amp With Disable
• Manufacturer: National Semiconductor Corporation

Description
The CLC411 is a high-speed current-feedback operational
amplifier which operates from ±15V power supplies.
The external supplies (±V
voltages internally. The amplifier itself sees
approximately ±6.5V rails. Thus the device yields
performance comparable to Comlinear’s ±5V devices,
but with higher supply voltages. There is no degradation
in rated specifications when the CLC411 is operated
from ±12V. A slight reduction in bandwidth will be
observed with ±10V supplies. Operation at less than
±10V is not recommended.
A block diagram of the amplifier and regulator topology
is shown in Figure 2, “CLC411 Equivalent Circuit.” The
regulators derive their reference voltage from an internal
floating zener voltage source. External control of the
zener reference pins can be used to level-shift amplifier
operation which is discussed in detail in the section
entitled “Extending Input/Output Range with V
Power Supply Decoupling
There are four pins associated with the power supplies.
The V
V
Figures 1 and 3 , “Recommended Non-inverting Gain
Circuit” and "Recommended Inverting Gain Circuit"
show the recommended supply decoupling scheme
with four ceramic and two electrolytic capacitors. The
ceramic capacitors must be placed immediately adjacent
to the device pins and connected directly to a good
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r
pins (5,1) are connected to internal reference nodes.
V
CC
in
pins (4,7) are the external supply voltages. The
R
in
3
2
Figure 2: CLC411 Equivalent Circuit
R
g
-
+
reg
reg
+
_
6.8 F
3
2
0.1 F
6.8 F
0.1 F
+
_
CLC411
7
4
-V
+V
8
cc
6
cc
+V
5
-V
1
CC
r
17k
17k
r
) are regulated to lower
0.01 F
0.01 F
6
Figure 1: Recommended
Non-inverting Gain Circuit
R
f
+
-
V
DIS
1
5
4
7
z
+V
+V
-V
-V
r
cc
cc
r
V
out
r
.”
4
low-inductance ground plane. Bypassing the V
reduce high frequency noise (>10MHz) in the amplifier.
If this noise is not a concern these capacitors may be
eliminated.
Differential Gain and Phase
The differential gain and phase errors of the CLC411
driving one doubly-terminated video load (R
specified and guaranteed in the “Electrical
Characteristics” table. The “Typical Performance” plot,
“Differential Gain and Phase (4.43MHz)” shows the
differential gain and phase performance of the CLC411
when driving from one to four video loads. Application
note OA-08, “Differential Gain and Phase for Composite
Video Systems,” describes in detail the techniques
used to measure differential gain and phase.
Feedback Resistor
The loop gain and frequency response for a current-
feedback operational amplifier is determined largely by
the feedback resistor, R
and typical performance plots contained within the
datasheet, unless otherwise stated, specify an R
301 , a gain of +2V/V and operation with ±15V power
supplies. The frequency response at different gain
settings and supply voltages can be optimized by
selecting a different value of R
will peak the frequency response and extend the
bandwidth while increasing its value will roll off the
response. For unity-gain voltage follower circuits, a
Figure 3: Recommended
Inverting Gain Circuit
500
400
300
200
100
V
0
in
Figure 4: Recommended R
0
R
T
1
2
R
g
25
3
f
. The electrical characteristics
Gain (V/V)
4
3
2
6.8 F
0.1 F
6.8 F
0.1 F
5
Inverting
+
_
CLC411
7
f
. Generally, lowering R
6
4
+V
-V
8
cc
cc
Non-Inverting
7
+V
f
5
-V
1
vs. Gain
r
r
8
0.01 F
0.01 F
Select R
6
R
9
R
f
in
L
=150 ) are
10
= R
T
DIS
r
to yield
T
pins will
||R
g
V
out
f
of
f