ADA4891-2ARZ Analog Devices Inc, ADA4891-2ARZ Datasheet - Page 12

• Manufacturer Part Number: ADA4891-2ARZ
• Description: Lw Cst CMOS Hgh Spd RR Amp
• Manufacturer: Analog Devices Inc

Specifications of ADA4891-2ARZ

• Amplifier Type: General Purpose
• Number Of Circuits: 2
• Output Type: Rail-to-Rail
• Slew Rate: 210 V/µs
• -3db Bandwidth: 240MHz
• Current - Input Bias: 2pA
• Voltage - Input Offset: 2500µV
• Current - Supply: 4.4mA
• Current - Output / Channel: 150mA
• Voltage - Supply, Single/dual (±): 2.7 V ~ 5.5 V, ±1.35 V ~ 2.75 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Gain Bandwidth Product: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADA4891-1/ADA4891-2
APPLICATIONS INFORMATION
USING THE ADA4891
Understanding the subtleties of the ADA4891 family gives users
insight into how to exact its peak performance. In this section, how
the gain, component values, and parasitics affect the performance
of the ADA4891 are discussed. The wideband, noninverting
configuration of the ADA4891 is shown in Figure 41, while the
wideband, inverting configuration of the ADA4891 is shown
in Figure 42.
WIDEBAND, NONINVERTING OPERATION
In Figure 41, R
respectively. Together, R
amplifier, and the value of R
effect of R
of R
from 549 Ω to 698 Ω.
In a controlled impedance signal path, R
termination resistor designed to match that of the input source
impedance. Note that it is not required for normal operation.
R
Table 4. Recommended Values for the ADA4891-1/ADA4891-2 Performance
Gain
−1
+1
+2
+5
+10
T
is generally set to match the input source impedance.
F
on 0.1 dB Gain Flatness section. Typical R
R
604
0
604
604
604
F
SOURCE
F
on the 0.1 dB gain flatness is discussed in the Effect
V
50Ω
Feedback Network Values
I
F
and R
Figure 41. Noninverting Configuration
G
R
denote the feedback and the gain resistor,
T
F
0.1µF
and R
R
G
R
604
0
604
151
67.1
F
ADA4891-1
G
defines the 0.1 dB bandwidth. The
G
–V
+V
determine the noise gain of the
S
S
0.1µF
R
F
10µF
T
is used as the input
V
O
−3 dB Small Signal Bandwidth (MHz)
V
118
236
120
32.5
12.7
10µF
F
OUT
R
values range
L
= 200 mV p-p
Rev. A | Page 12 of 20
WIDEBAND, INVERTING GAIN OPERATION
Figure 42 shows the inverting gain configuration. To match the
input source impedance for the inverting gain configuration, set
the parallel combination of R
source impedance.
Note that a bias current cancellation resistor is not required in
the noninverting input of the amplifier because the input bias
current of the ADA4891 is very low (less than 10 pA). Therefore,
the dc errors caused by the bias current are negligible.
For both configurations, it is often useful to increase the R
to decrease the loading on the output. Increasing the R
improves the harmonic distortion at the expense of reducing
the 0.1 dB bandwidth of the amplifier. This effect is discussed
further in the Effect of R
RECOMMENDED VALUES
Table 4 provides a handy reference for various configurations
and shows the effect of gain on the −3 dB small signal bandwidth,
slew rate, and peaking of the ADA4891-1/ADA4891-2. Note
that as the gain increases, the small signal bandwidth decreases
as is expected from the gain bandwidth product relationship. In
addition, the phase margin improves with higher gains, and the
amplifier becomes more stable. As a result, the peaking in the
frequency response is reduced (see Figure 6).
SOURCE
V
50Ω
I
t
188
154
178
149
71
R
Figure 42. Inverting Configuration
R
Slew Rate (V/μs)
R
T
G
F
on 0.1 dB Gain Flatness section.
T
t
192
263
204
154
72
ADA4891-1
//R
F
+V
–V
G
to match that of the input
S
S
0.1µF
0.1µF
R
F
Peaking (dB)
1.3
2.6
1.4
0
0
V
O
10µF
10µF
R
L
F
F
value
value