Datasheet
Data Sheet AD8029/AD8030/AD8040
Rev. B | Page 17 of 24
APPLICATIONS
WIDEBAND OPERATION
+V
S
–V
S
C2
10µF
C1
0.1µF
C4
0.1µF
C3
10µF
V
OUT
+
–
AD8029
R
G
R1
R
F
DISABLE
V
IN
R1 = R
F
||R
G
03679-0-052
Figure 51. Wideband Non-inverting Gain Configuration
+V
S
–V
S
C1
0.1µF
C4
0.1µF
C3
10µF
R1
V
OUT
–
+
AD8029
R
G
R1 = R
F
||R
G
R
F
V
IN
03679-0-053
C2
10µF
DISABLE
Figure 52. Wideband Inverting Gain Configuration
OUTPUT LOADING SENSITIVITY
To achieve maximum performance and low power dissipation,
the designer needs to consider the loading at the output of
AD8029/AD8030/AD8040. Table 5 shows the effects of output
loading and performance.
When operating at unity gain, the effective load at the amplifier
output is the resistance (R
L
) being driven by the amplifier. For
gains other than 1, in noninverting configurations, the feedback
network represents an additional current load at the amplifier
output. The feedback network (R
F
+ R
G
) is in parallel with R
L
,
which lowers the effective resistance at the output of the
amplifier. The lower effective resistance causes the amplifier to
supply more current at the output. Lower values of feedback
resistance increase the current draw, thus increasing the
amplifier’s power dissipation.
For example, if using the values shown in Table 5 for a gain of 2,
with resistor values of 2.5 kΩ, the effective load at the output is
1.67 kΩ. For inverting configurations, only the feedback resistor
R
F
is in parallel with the output load. If the load is greater than
that specified in the data sheet, the amplifier can introduce
nonlinearities in its open-loop response, which increases
distortion. Figure 53 and Figure 54 illustrate effective output
loading and distortion performance. Increasing the resistance of
the feedback network can reduce the current consumption, but
has other implications.
FREQUENCY (MHz)
HARMONIC DISTORTION (dBc)
0.01
–120
0.1 1.0 10
03679-A-008
–40
–50
–60
–70
–80
–90
–100
–110
V
S
= 5V
V
OUT
= 0.1V p-p
R
L
= 5kΩ
R
L
= 2.5kΩ
V
S
= 5V
V
OUT
= 2.0V p-p
SECOND HARMONIC – SOLID LINES
THIRD HARMONIC – DOTTED LINES
R
L
= 1kΩ
Figure 53. Gain of 1 Distortion
FREQUENCY (MHz)
HARMONIC DISTORTION (dBc)
0.01
–120
0.1 1.0 10
03679-A-009
–40
–50
–60
–70
–80
–90
–100
–110
V
S
= 5V
V
OUT
= 0.1V p-p
R
F
= R
L
= 1kΩ
V
S
= 5V
V
OUT
= 2.0V p-p
SECOND HARMONIC – SOLID LINES
THIRD HARMONIC – DOTTED LINES
R
F
= R
L
= 5kΩ
R
F
= R
L
= 2.5kΩ
Figure 54. Gain of 2 Distortion