clc430 National Semiconductor Corporation, clc430 Datasheet - Page 5

• Manufacturer Part Number: clc430
• Description: General Purpose 100mhz Op Amp With Disable
• Manufacturer: National Semiconductor Corporation

General Design Considerations
The CLC430 is a general purpose current-feedback ampli-
fier for use in a variety of small- and large-signal applica-
tions. Use the feedback resistor to fine tune the gain
flatness and -3dB bandwidth for any gain setting. Com-
linear provides information for the performance at a gain of
+2 for small and large signal bandwidths. The plots show
feedback resistor values for selected gains.
Gain
Use the following equations to set the CLC430's non-
inverting or inverting gain:
Choose the resistor values for non-inverting or inverting
gain by the following steps.
1) Select the recommended feedback resistor R
2) Choose the value of R
3) Select R
4) Select R
High Gains
Current feedback closed-loop bandwidth is independent of
gain-bandwidth-product for small gain changes. For larger
gain changes the optimum feedback register R
by the following:
As gain is increased, the feedback resistor allows bandwidth
to be held constant over a wide gain range. For a more
complete explanation refer to application note OA-25 Stabil-
ity Analysis of Current-Feedback Amplifiers.
Resistors have varying parasitics that affect circuit perfor-
mance in high-speed design. For best results, use leaded
metal-film resistors or surface mount resistors. A SPICE
model for the CLC430 is available to simulate overall
circuit performance.
Enable / Disable Function
The CLC430 amplifier features an enable/disable function
that changes the output and inverting input from low to high
impedance. The pin 8 enable/disable logic levels are as
to plot in the plot section entitled R
Non -Inverting Gain = 1+
Inverting Gain = -
V
in
Fig. 0 Component Identification
in
s
to set the circuit output impedance.
for input impedance and input bias.
R
R
in
f
R
g
724
+
-
CLC430
R
g
f
R
R
to set gain.
60
g
f
A
R
R
v
g
f
R
f
s
vs Gain ).
V
out
f
is derived
f
(refer
5
follows:
The amplifier is enabled with pin 8 left open due to the 2k
pull-up resistor, shown in Fig. 1.
Open-collector or CMOS interfaces are recommended to
drive pin 8. The turn-on and off time depends on the speed
of the digital interface.
The equivalent output impedance when disabled is shown
in Fig. 2. With R
R
ance. To raise the output impedance in the disabled state,
connect the CLC430 as a unity-gain voltage follower by
removing R
mended R
circuit layouts consider using the dual CLC431 (with
disable) or the dual CLC432 (without disable).
2
To meet low distortion requirements, recognize the effect
of the feedback resistor. Increasing the feedback resistor
will decrease the loop gain and increase distortion. De-
creasing the load impedance increases 3
distortion more than 2
Differential Gain and Differential Phase
The CLC430 has low DG and DP errors for video applica-
tions. Add an external pulldown resistor to the CLC430’s
output to improve DG and DP as seen in Fig.3. A 604 R
will improve DG and DP to 0.01% and 0.02°.
nd
g
dominates and reduces the disabled output imped-
and 3
Fig. 2 Equivalent Disabled Output Impedance
V
Enable
Disable
Fig. 1 Pin 8 Equivalent Disable Circuit
cc
rd
f
in a unity-gain follower circuit. For high density
g
. Current-feedback op-amps need the recom-
Harmonic Distortion
V
Pin 8 DISABLE
in
g
2k
8k
R
connected to ground, the sum of R
g
±15V
>12.7V
<10.0V
+
nd
-
.
300k
8pF
R
f
Equivalent Impedance
in Disable
+ V
- V
To CLC430
Bias network
cc
cc
±5V
>2.7V
<0.8V
http://www.national.com
V
out
rd
harmonic
f
and
P