AD8352ACPZ-R7 datasheet(11/20 Pages) AD

11 / 20 page

AD8352

Rev. 0| Page 11 of 20

APPLICATIONS

Table 7. Broadband Selection of RG, CD, and RD: 1 kΩ Load

GAIN AND DISTORTION ADJUSTMENT

(DIFFERENTIAL INPUT)

AV (dB)

RG (Ω)

CD (pF)

RD (kΩ)

750

0 (DNP)

6.8

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.

()(

)

ial

VDifferent

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

430

500

(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)

390

0 (DNP)

6.8

220

0 (DNP)

4.3

140

0.1

4.3

115

0.2

4.3

0.3

4.3

0.6

4.3

360

0 (DNP)

6.8

210

0 (DNP)

6.8

180

0.05

6.8

130

0.1

6.8

0.3

6.8

0.5

6.8

400

RG (Ω)

100

200

300

150

250

350

Figure 20. RG vs. Gain, RL = 200 Ω

CD (pF)

0.2

0.4

0.6

0.8

1.0

0.1

0.3

0.5

0.7

0.9

Figure 21. CD vs. Gain, RL = 200 Ω

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