AD8022

Rev. B | Page 15 of 16

191

Ω

1%

191

Ω

1%

243

Ω

1%

243

Ω

1%

249

Ω

1%

422

Ω

1%

249

Ω

1%

COMMON-

MODE

VOLTAGE

8200pF

10%

8200pF

10%

6800pF

5% NPO

6800pF

5% NPO

0.1

μF

50V

5%

NPO

0.1

μF

16V

10%

X7R

AD8022

12V

3

2

8

1

AD8022

6

5

4

7

Figure 41. Differential Input Sallen-Key Filter

Using AD8022 on Single Supply, +12 V

FREQUENCY (Hz)

7.5

–42.5

–37.5

–32.5

–27.5

–22.5

–17.5

–12.5

–7.5

–2.5

2.5

10k

10M

1M

100k

Figure 42. Frequency Response of Sallen-Key Filter

LAYOUT CONSIDERATIONS

As is the case with all high speed amplifiers, careful attention to

printed circuit board layout details prevent associated board

parasitics from becoming problematic. Proper RF design

technique is mandatory. The PCB should have a ground plane

covering all unused portions of the component side of the

board to provide a low impedance return path. Removing the

ground plane from the area near the input signal lines reduces

stray capacitance. Chip capacitors should be used for supply

bypassing. One end of the capacitor should be connected to the

ground plane, and the other should be connected no more than

1/8 inch away from each supply pin. An additional large

(0.47 μF to 10 μF) tantalum capacitor should be connected in

parallel, although not necessarily as close, in order to supply

current for fast, large signal changes at the AD8022 output.

Signal lines connecting the feedback and gain resistors should

be as short as possible, minimizing the inductance and stray

capacitance associated with these traces. Locate termination

resistors and loads as close as possible to the input(s) and

output, respectively. Adhere to stripline design techniques for

long signal traces (greater than about 1 inch). Following these

generic guidelines improves the performance of the AD8022 in

all applications.