AD8432ACPZ-R7 datasheet(20/28 Pages) AD

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AD8432

Rev. 0 | Page 20 of 28

The user must determine the level of matching accuracy desired

and adjust RFB accordingly. The RFB and CFB network presents a

load to OPL that OPH does not see. The user may add an identical

load on OPH, to improve slightly the distortion caused by this

imbalance.

There is a feedback capacitor (CFB) in series with RFB (see Figure 60)

because the dc levels of the positive output and the positive input

are different. At higher frequencies, the value of the feedback

capacitor needs to be considered.

The unterminated bandwidth (RFB = ∞) is 200 MHz. The AD8432

has a low input referred voltage noise of 0.85 nV/√Hz at the

lowest gain, 12.04 dB (unterminated configuration). To achieve

such low noise, the dual amplifier consumes 24 mA, resulting in

a power consumption of 120 mW.

Table 6. Feedback Resistance for Several RIN and Gain Combinations

Desired RIN (Ω)

Differential Gain (V/V)

Single-Ended Gain,

G/2 (V/V)

Exact RFB (Ω),

Equation 2

RFB (Ω), 1% Standard Value

Actual RIN (Ω),

Equation 2

151.2

150

49.6

227.8

226

74.4

100

304.9

301

98.7

200

620

619

199.7

1 k

3.58 k

3.57 k

998.4

252

250

49.6

100

508.2

511

100.5

352.9

357

50.6

100

711.5

715

100.5

453.7

453

49.9

100

914.8

909

99.4

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