AD8352 데이터 시트보기 (PDF) - Analog Devices
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AD8352 Datasheet PDF : 19 Pages
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Data Sheet
APPLICATIONS INFORMATION
GAIN AND DISTORTION ADJUSTMENT
(DIFFERENTIAL INPUT)
Table 5 and Table 6 show the required value of RG for the gains
specified at 200 Ω and 1 kΩ loads. Figure 22 and Figure 24 plot
gain vs. RG up to 18 dB for both load conditions. For other output
loads (RL), use Equation 1 to compute gain vs. RG.
AV
Differential
=
RG+ 500
(RG+ 5) (RL+ 53) +
430
RL
(1)
where
RL is the single-ended load.
RG is the gain setting resistor.
The third-order harmonic distortion can be reduced by using
external components RD and CD. Table 5 and Table 6 show the
required values for RD and CD for the specified gains to achieve
(single tone) third-order distortion reduction at 180 MHz.
Figure 23 and Figure 25 show any gain (up to 18 dB) vs. CD for
200 Ω and 1 kΩ loads, respectively. When these values are selected,
they result in minimum single tone, third-order distortion at
180 MHz. This frequency point provides the best overall broad-
band distortion for the specified frequencies below and above
this value. For applications above ~300 MHz, CD and RD are
not required. See the Specifications section and the third-order
harmonic plots for more details (see Figure 12, Figure 14, and
Figure 15).
CD can be further optimized for narrow-band tuning requirements
below 180 MHz that result in relatively lower third-order (in-
band) intermodulation distortion terms. See the Narrow-Band,
Third-Order Intermodulation Cancellation section for more
information. Though not shown, single tone, third-order
optimization can also be improved for narrow-band frequency
applications below 180 MHz with the proper selection of CD,
and 3 dB to 6 dB of relative third-order improvement can be
realized at frequencies below approximately 140 MHz.
Using the information listed in Table 5 and Table 6, an extrapolated
value for RD can be determined for loads between 200 Ω and 1 kΩ.
For loads above 1 kΩ, use the 1 kΩ RD values listed in Table 6.
Table 5. Broadband Selection of RG, CD, and RD, 200 Ω Load
AV (dB)
3
RG (Ω)
390
CD (pF)
Open
RD (kΩ)
6.8
6
220
Open
4.3
9
140
0.1
4.3
10
115
0.2
4.3
12
86
0.3
4.3
15
56
0.6
4.3
18
35
1
4.3
AD8352
Table 6. Broadband Selection of RG, CD, and RD, 1 kΩ Load
AV (dB)
RG (Ω)
CD (pF)
RD (kΩ)
3
750
Open
6.8
6
360
Open
6.8
9
210
Open
6.8
10
180
0.05
6.8
12
130
0.1
6.8
15
82
0.3
6.8
18
54
0.5
6.8
20
18
16
14
12
10
8
6
4
2
0
0
50 100 150 200 250 300 350 400
RG (Ω)
Figure 22. Gain vs. RG, RL = 200 Ω
20
18
16
14
12
10
8
6
4
2
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
CD (pF)
Figure 23. Gain vs. CD, RL = 200 Ω
Rev. C | Page 11 of 19
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