clc411 National Semiconductor Corporation, clc411 Datasheet - Page 6

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

than one volt. Single-ended ECL, Figure 5C, maintains
this desired maximum differential input voltage. TTL
and CMOS have higher V
circuit of figure 5D will ensure the voltage applied
between the bases of Q1 and Q2 does not cause
excessive switching delays in the CLC411. Under the
above proscribed four-transistor interface, all variations
were evaluated with approximately 1ns rise and fall
times which produced switching speeds equivalent to
the rated disable/enable switching times found in the
"CLC411 Electrical Characteristics" table.
A general multiplexer configuration using several
CLC411s is illustrated in figure 6, where a typical 8-to-
1 digital mux is used to control the switching operation
of the paralleled CLC411s. Since "break-before-make"
is a guaranteed specification of the CLC411 this
configuration works nicely. Notice the buffers used in
driving the disable pins of the CLC411s. These buffers
may be 15V CMOS logic devices mentioned previously
or any variation of the four-transistor comparator
illustrated above.
Extending Input/Output Range with V
As can be seen in Figure 3, the magnitude of the internal
regulated supply voltages is fixed by V
operation, with ±15V external supplies,
+
range) and VO (output voltage range, no load) are
specified under these conditions. These parameters
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9V when left floating. CMIR (common mode input
-10
Figure 7: DC Parameters as a Function of +V
-5
-10
-15
20
15
10
-5
5
high
V
V
cm
cm
to V
+
5
_
+V
low
CC
max
excursions. The
10
+
V
r
r
z
is nominally
. In normal
+VO
-VO
r
15
-V
min
max
CC
+V
max
r
6
implicitly have 0V as their midpoint, i.e. the VO range
is ±6V, centered at 0V.
An external voltage source can be applied to
the range of the input/output voltages. For example, if
it were desired to move the positive VO range from
to a
Parameters as a Function of
the required supply and
Figure 7, locate the point on the
ordinate is
intersecting the other lines in the graph. The circuit
voltages are the ordinates of these intersections. For
this example these points are shown in the graph as
solid dots. The required voltage sources are
+
reference voltages are applied, the range for VO is -3V
to
between the minimum and maximum voltages is
constant, i.e. 12V for VO, only the midpoint has been
shifted, i.e. from 0V to
Note that in this example the -V
(or bypassed to reduce high-frequency noise). The
difference between
shifting voltage can be applied to only one of the
reference pins, not both. If extended operation were
needed in the negative direction, Figure 4 may be used
by changing the signs, and applying the resultant
negative voltage to the -V
+
shifts of input/output voltage range.
Printed Circuit Layout & Evaluation Board
Refer to application note OA-15, “Frequent Faux Pas in
Applying Wideband Current Feedback Amplifiers,” for
board layout guidelines and construction techniques. Two
very important points to consider before creating a layout
which are found in the above application note are worth
reiteration. First the input and output pins are sensitive to
parasitic capacitances. These parasitic capacitances
can cause frequency-response peaking or sustained
oscillation. To minimize the adverse effect of parasitic
capacitances, the ground plane should be removed from
those pins to a distance of at least 0.25" Second, leads
should be kept as short as possible in the finished layout.
In particular, the feedback resistor should have its shortest
lead on the inverting input side of the CLC411. The output
is less sensitive to parasitic capacitance and therefore
can drive the longer of the two feedback resistor
connections. The evaluation board available for the CLC411
(part #730013 for through-hole packages, 730027 for SO-
8) may be used as a reference for proper board layout.
Application schematics for this evaluation board are in the
product accessories section of the Comlinear databook.
V
V
+
r
CC
9V, and CMIR ranges from -1V to
+
be used for positive shifts, and -V
=
9V maximum in unipolar operation, Figure 7, “DC
+
12V, -V
+
9V. Draw a vertical line from this point
CC
=-12V. When these supply and
+
V
r
+
and -V
3V for VO.
r
+
pin. It is recommended that
V
+
r
V
r
voltages. Referring to
r
r
”, is used to determine
is fixed by V
pin has been left open
+
VO
+
7V. The difference
MAX
line where the
r
for negative
+
+
z
V
V
. A level-
r
r
=
to shift
+
12V,
+
6V