AD8051 Analog Devices, AD8051 Datasheet - Page 18

• Manufacturer Part Number: AD8051
• Description: Low Cost, High Speed, Single, Rail-to-Rail Amplifier
• Manufacturer: Analog Devices

Specifications of AD8051

• -3db Bandwidth: 110MHz
• Slew Rate: 170V/µs
• Vos: 1.7mV
• Ib: 1.4µA
• # Opamps Per Pkg: 1
• Input Noise (nv/rthz): 16nV/rtHz
• Vcc-vee: 3V to 12V
• Isy Per Amplifier: 5.5mA
• Packages: SOIC,SOT

AD8051/AD8052/AD8054
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
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noise bandwidth of the analog signal before analog-to-digital
conversion.
Note that the unused amplifier’s inputs should be tied to ground.
V
The frequency response of the circuit is shown in Figure 47.
IN
3kΩ
R1
Figure 47. Frequency Response of 2 MHz Band-Pass Biquad Filter
–10
–20
–30
–40
0
10k
2
3
Figure 46. 2 MHz Biquad Band-Pass Filter Using AD8054
50pF
AD8054
2kΩ
C1
R2
1
2kΩ
R3
100k
6
5
AD8054
1kΩ
2kΩ
FREQUENCY (Hz)
R4
R6
7
1M
2kΩ
R5
10
9
50pF
AD8054
C2
10M
8
13
BAND-PASS
FILTER OUTPUT
12
100M
14