AD8352 datasheet(12/20 Pages) AD

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AD8352

Rev. 0| Page 12 of 20

800

RG (Ω)

100

200

300

400

500

600

700

Figure 22. RG vs. Gain, RL = 1 kΩ

00.5

CD (pF)

0.1

0.2

0.3

0.4

Figure 23. CD vs. Gain, RL = 1 kΩ

SINGLE-ENDED INPUT OPERATION

The AD8352 can be configured as a single-ended to differential

amplifier as shown in Figure 24. To balance the outputs when

driving only the VIP input, an external resistor (RN) of 200 Ω is

added between VIP and RGN. See Equation 2 to determine the

single-ended input gain (AVSingle-ended) for a given RG or RL.

()(

)

430

500

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

−

ended

VSingle

(2)

where:

RL = single-ended load.

RG = gain setting resistor.

Figure 25 plots gain vs. RG for 200 Ω and 1 kΩ loads. Table 8

and Table 9 show the values of CD and RD required (for 180 MHz

broadband third-order, single tone optimization) for 200 Ω and

1 kΩ loads, respectively. This single-ended configuration

provides −3 dB bandwidths similar to input differential drive.

Figure 26 through Figure 28 show distortion levels at a gain of

12 dB for both 200 Ω and 1 kΩ loads. Gains from 3 dB to 18 dB,

using optimized CD and RD values, obtain similar distortion

levels.

25Ω

65Ω

50Ω

0.1µF

RGP

RGN

AD8352

VIP

200Ω

Figure 24. Single-Ended Schematic

10k

RG (Ω)

100

GAIN, RL =1kΩ

GAIN, RL =200Ω

Figure 25. Gain vs. RG

–60

–110

FREQUENCY (MHz)

140

190

240

–70

–80

–90

–100

2NDS, 2V p-p OUT

2NDS, 1V p-p OUT

Figure 26. Single-Ended, Second-Order Harmonic Distortion,

200 Ω Load

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 CD and RD specified in

Table 8 and Table 9. As with differential input drive, relative

third-order reduction improvement at frequencies below

140 MHz are realized with proper selection of CD and RD.

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