AD8051ARTZ-R2 datasheet(18/24 Pages) AD

18 / 24 page

AD8051/AD8052/AD8054

Rev. H | Page 18 of 24

LAYOUT CONSIDERATIONS

The specified high speed performance of the AD8051/AD8052/

AD8054 requires careful attention to board layout and component

selection. Proper RF design techniques and low parasitic

component selection are necessary.

The PCB should have a ground plane covering all unused

portions of the component side of the board to provide a low

impedance path. The ground plane should be removed from the

area near the input pins to reduce parasitic capacitance.

Chip capacitors should be used for supply bypassing. One end

should be connected to the ground plane and the other within

3 mm of each power pin. An additional large (4.7 μF to 10 μF)

tantalum electrolytic capacitor should be connected in parallel,

but not necessarily so close, to supply current for fast, large

signal changes at the output.

The feedback resistor should be located close to the inverting

input pin to keep the parasitic capacitance at this node to a

minimum. Parasitic capacitance of less than 1 pF at the inverting

input can significantly affect high speed performance.

Stripline design techniques should be used for long signal traces

(greater than about 25 mm). These should be designed with a

characteristic impedance of 50 Ω or 75 Ω and be properly

terminated at each end.

ACTIVE FILTERS

Active filters at higher frequencies require wider bandwidth op

amps to work effectively. Excessive phase shift produced by

lower frequency op amps can significantly affect active filter

performance.

Figure 46 shows an example of a 2 MHz biquad bandwidth filter

that uses three op amps of an AD8054. Such circuits are

sometimes used in medical ultrasound systems to lower the

noise bandwidth of the analog signal before analog-to-digital

conversion.

Note that the unused amplifier’s inputs should be tied to ground.

AD8054

1kΩ

2kΩ

3kΩ

50pF

VIN

BAND-PASS

FILTER OUTPUT

Figure 46. 2 MHz Biquad Band-Pass Filter Using AD8054

The frequency response of the circuit is shown in Figure 47.

FREQUENCY (Hz)

–10

–20

–30

–40

10k

100k

10M

100M

Figure 47. Frequency Response of 2 MHz Band-Pass Biquad Filter

AD8051ARTZ-R2 数据表(PDF) 18 Page - Analog Devices

AD8051ARTZ-R2 数据表(HTML) 18 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

数据表下载