AD8352(Rev0) データシートの表示（PDF） - Analog Devices
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AD8352 Datasheet PDF : 20 Pages
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AD8352
APPLICATIONS
GAIN AND DISTORTION ADJUSTMENT
(DIFFERENTIAL INPUT)
Table 6 and Table 7 show the required value of RG for the gains
specified at 200 Ω and 1 kΩ loads. Figure 20 and Figure 22 plot
RG vs. gain up to 18 dB for both load conditions. For other
output loads (RL), use Equation 1 to compute gain vs. RG.
AVDifferential
=
⎜⎜⎝⎛ (RG
+
RG +
5)(RL
500
+ 53)
+
430
⎟⎟⎠⎞RL
(1)
where:
RL = single-ended load.
RG = gain setting resistor.
The third-order harmonic distortion can be reduced by using
external components RD and CD. Table 6 and Table 7 show the
required values for RD and CD vs. the specified gains to achieve
(single tone) third-order distortion reduction at 180 MHz.
Figure 21 and Figure 23 show CD vs. any gain (up to 18 dB) 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 broadband distortion for the specified frequencies below
and above this value. For applications above approximately
300 MHz, CD and RD are not required. See the Specifications
section and third-order harmonic plots in the Typical
Performance Characteristics section for more details.
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 6 and Table 7, 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 7.
Table 6. Broadband Selection of RG, CD, and RD: 200 Ω Load
AV (dB)
RG (Ω)
CD (pF)
RD (kΩ)
3
390
0 (DNP)
6.8
6
220
0 (DNP)
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
Table 7. Broadband Selection of RG, CD, and RD: 1 kΩ Load
AV (dB)
RG (Ω)
CD (pF)
RD (kΩ)
3
750
0 (DNP)
6.8
6
360
0 (DNP)
6.8
9
210
0 (DNP)
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 20. RG vs. Gain, 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 21. CD vs. Gain, RL = 200 Ω
Rev. 0| Page 11 of 20
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