CLC412AJP National Semiconductor, CLC412AJP Datasheet - Page 11

• Manufacturer Part Number: CLC412AJP
• Description: IC OP AMP VIDEO DUAL 8-DIP
• Manufacturer: National Semiconductor

Specifications of CLC412AJP

• Applications: Current Feedback
• Number Of Circuits: 2
• -3db Bandwidth: 250MHz
• Slew Rate: 1300 V/µs
• Current - Supply: 10.2mA
• Current - Output / Channel: 70mA
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *CLC412AJP

Feedback Resistor Selection
The loop gain and frequency response for a current-
feedback operational amplifier is determined largely by the
feedback resistor, R
Typical Performance plots specify an R
+2V/V and operation with
erwise stated). Generally, lowering R
value will peak the frequency response and extend the band-
width while increasing its value will roll off the response.
Reducing the value of R
value will cause overshoot, ringing and eventually oscillation.
The plot above labeled “Frequency Response vs. R
the CLC412’s frequency and phase response as R
while the gain remains constant at +2V/V (R
plot shows that one particular value of R
frequency and phase response at the specified gain setting,
i.e. 634
unlike voltage-feedback op amps, have a direct relationship
between their frequency and phase response to the value of
the feedback resistor, R
tion Note OA-13 which describes the relationship between R
and closed-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.
R
at a gain of +2V/V. Current-feedback op amps,
f
vs. Non-Inverting Gain (AJE & AJP)
Frequency Response vs. R
f
. The Electrical Characteristics and
f
. For more information see Applica-
f
±
too far below its recommended
5V power supplies (unless oth-
f
from its recommended
f
of 634 , a gain of
f
will optimize the
f
L
= 100 ). This
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f
is varied
f
” shows
f
11
Both plots show the value of R
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
limitation placed on R
to the desire to keep R
inverting input resistance. Therefore, the resulting small-
signal bandwidth curves, labeled “BW”, correspond to the
two (solid) “R
produced by the analysis of OA-13 since these plots were
produced from an actual board layout that included parasitic
capacitances not accounted for by the analysis of OA-13. It
should be noted that a non-inverting gain of +1V/V requires
an R
2V
In order to bandlimit the CLC412 at any particular gain
setting, a larger value of R
the plots above) is needed. Following the analysis in OA-13,
we find the CLC412’s “optimum feedback transimpedance”,
Z
The “optimum feedback transimpedance” is unique for each
current-feedback op amp and determines the recommended
value of R
line on the “Open-loop Transimpedance, Z(s)” plot from
57.5dB (on the left vertical axis), we find the intersection with
the transimpedance magnitude trace occurs at a frequency
of 180MHz. This frequency is only an approximation of the
CLC412’s small-signal bandwidth. From this intersection,
one can see that an increase in Z
intersection occurring at a lower frequency. This is the pro-
cess to follow when bandlimiting. Once the target small-
signal bandwidth is determined, the new value of Z
off the graph at the point where this frequency and the
transimpedance magnitude trace intersect. One can then
t
*
PP
, below.
f
.
= 1k
f
for a particular gain setting. Drawing a horizontal
R
f
f
and the output voltage used for both plots is
” curves. These results may deviate from that
vs. Inverting Gain (AJE & AJP)
g
(i.e., R
g
f
greater in value than that of the
(than previously recommended in
>
g
A
V
50 ). This limitation is due
f
approaching a non-zero
>
t
+6) results from the
will produce a new
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t
is picked