Datasheet

AD8352
Rev. B | Page 13 of 20
This broadband optimization was also performed at 180 MHz.
As with differential input drive, the resulting distortion levels
at lower frequencies are based on the C
D
and R
D
specified in
Table 7 and Table 8. As with differential input drive, relative
third-order reduction improvement at frequencies below
140 MHz is realized with proper selection of C
D
and R
D
.
–
60
–110
FREQUENCY (MHz)
HD3 (dBc)
10 70 140 190 240
–70
–80
–90
–100
2V p-p OUT
1V p-p OUT
05728-022
Figure 29. Single-Ended, Third-Order Harmonic Distortion (HD3) vs.
Frequency, 200 Ω Load
–
60
–110
FREQUENCY (MHz)
HD2 (dBc)
10 70 140 190 240
–70
–80
–90
–100
1V p-p OUT
2V p-p OUT
05728-023
Figure 30. Single-Ended, Second-Order Harmonic Distortion (HD2) vs.
Frequency, 1 kΩ Load
–
60
–110
FREQUENCY (MHz)
HD3 (dBc)
10 70 140 190 240
–70
–80
–90
–100
1V p-p OUT
2V p-p OUT
05728-025
Figure 31. Single-Ended, Third-Order Harmonic Distortion (HD3) vs.
Frequency, 1 kΩ Load
Table 7. Distortion Cancellation Selection Components
(R
D
and C
D
) for Required Gain, 200 Ω Load
A
V
(dB) R
G
(Ω) C
D
(pF) R
D
(kΩ)
3 4.3 k Open 4.3
6 540 Open 4.3
9 220 0.1 4.3
12 120 0.3 4.3
15 68 0.6 4.3
18 43 0.9 4.3
Table 8. Distortion Cancellation Selection Components
(R
D
and C
D
) for Required Gain, 1 kΩ Load
A
V
(dB) R
G
(Ω) C
D
(pF) R
D
(kΩ)
6 3 k Open 4.3
9 470 Open 4.3
12 210 0.2 4.3
15 120 0.3 4.3
18 68 0.5 4.3
NARROW-BAND, THIRD-ORDER
INTERMODULATION CANCELLATION
Broadband single tone, third-order harmonic optimization does
not necessarily result in optimum (minimum) two tone, third-
order intermodulation levels. The specified values for C
D
and
R
D
in Table 5 and Tabl e 6 were determined for minimizing
broadband, single tone third-order levels.
Due to phase-related distortion coefficients, optimizing single
tone third-order distortion does not result in optimum in-band
(2f
1
− f
2
and 2f
2
− f
1
), third-order distortion levels. By proper
selection of C
D
(using a fixed 4.3 kΩ R
D
), IP3s of better than
45 dBm are achieved. This results in degraded out-of-band,
third-order frequencies (f
2
+ 2f
1
, f
1
+ 2f
2
, 3f
1
and 3f
2
). Thus, careful
frequency planning is required to determine the trade-offs.
Figure 32 shows narrow-band (2 MHz spacing) OIP3 levels
optimized at 32 MHz, 70 MHz, 100 MHz, and 180 MHz using
the C
D
values specified in Figure 33. These four data points (the
C
D
value and associated OIP3 levels) are extrapolated to provide
close estimates of OIP3 levels for any specific frequency between
30 MHz and 180 MHz. For frequencies below ~140 MHz, narrow-
band tuning of OIP3 results in relatively higher OIP3s (vs. the
broadband results shown in Table 2 of the specifications). Though
not shown, frequencies below 30 MHz also result in improved
OIP3s when using proper values for C
D
.