clc412 National Semiconductor Corporation, clc412 Datasheet - Page 5

• Manufacturer Part Number: clc412
• Description: Dual Wideband Video Op Amp
• Manufacturer: National Semiconductor Corporation

Application Introduction
Offered in an 8-pin package for reduced space and cost,
the wideband CLC412 dual current-feedback op amp
provides closely matched DC & AC electrical performance
characteristics making the part an ideal choice for
wideband signal processing. Applications such as
broadcast-quality video systems, IQ amplifiers, filter
blocks, high-speed peak detectors, integrators and
transimpedance amplifiers will all find superior
performance in the CLC412 dual op amp.
Feedback Resistor Selection
The loop gain and frequency response for a current-
feedback operational amplifier is determined largely by
the feedback resistor, R
and Typical Performance plots specify an R
gain of +2V/V and operation with 5V power supplies
(unless otherwise stated). Generally, lowering R
recommended value will peak the frequency response
and extend the bandwidth while increasing its value will
roll off the response. Reducing the value of R
below its recommended value will cause overshoot,
ringing and eventually oscillation.
The plot above labeled "Frequency Response vs. R
shows the CLC412’s frequency and phase response as
R
(R
R
specified gain setting, i.e. 634
Current-feedback op amps, unlike voltage-feedback op
amps, have a direct relationship between their frequency
f
f
L
will optimize the frequency and phase response at the
is varied while the gain remains constant at +2V/V
=100 ). This plot shows that one particular value of
V
in
R
in
R
g
+V
-V
½CLC412
+
-
cc
cc
Figure 1
f
+
R
. The Electrical Characteristics
f
+
C
C
C
C
4
3
1
2
at a gain of +2V/V.
R
o
V
out
f
of 634 , a
f
f
from its
too far
f
"
5
and phase response to the value of the feedback resistor,
R
which describes the relationship between R
loop frequency response.
When configuring the CLC412 for other inverting or non-
inverting gains, it is necessary to adjust the value of the
feedback resistor in order to optimize the device’s
frequency and phase response. The two plots below
provide the means of selecting the recommended
feedback-resistor value for both inverting and non-
inverting gain selections. Both plots show the value of R
approaching a non-zero minimum (dashed line) at high
gains, which is characteristic of current-feedback op
amps, while the linear portion of the two (solid) curves
(i.e. -5>A
(i.e. R
R
resistance. Therefore, the resulting small-signal
f
g
. For more information see Application Note OA-13
greater in value than that of the inverting input
g
50 ). This limitation is due to the desire to keep
V
v
>+6) results from the limitation placed on R
in
R
R
g
b
+V
-V
Figure 2
½CLC412
-
+
cc
cc
+
R
f
+
C
C
C
C
2
4
3
1
R
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o
f
and closed-
V
out
g
f