AD8073JRZ Analog Devices Inc, AD8073JRZ Datasheet - Page 9

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AD8073JRZ

Manufacturer Part Number
AD8073JRZ
Description
IC,Operational Amplifier,TRIPLE,BIPOLAR,SOP,14PIN,PLASTIC
Manufacturer
Analog Devices Inc
Datasheet

Specifications of AD8073JRZ

Applications
Current Feedback
Number Of Circuits
3
-3db Bandwidth
100MHz
Slew Rate
500 V/µs
Current - Supply
3.5mA
Current - Output / Channel
30mA
Voltage - Supply, Single/dual (±)
5 V ~ 12 V, ±2.5 V ~ 6 V
Mounting Type
Surface Mount
Package / Case
14-SOIC (0.154", 3.90mm Width)
Lead Free Status / RoHS Status
Lead free / RoHS Compliant

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Quantity
Price
Part Number:
AD8073JRZ
Manufacturer:
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20 000
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Manufacturer:
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APPLICATIONS
Overdrive Recovery
Overdrive of an amplifier occurs when the output and/or input
range are exceeded. The amplifier must recover from this overdrive
condition and resume normal operation. As shown in Figure 4,
the AD8072 and AD8073 recover within 75 ns from positive
overdrive and 30 ns from negative overdrive.
Bandwidth vs. Feedback Resistor Value
The closed-loop frequency response of a current feedback amplifier
is a function of the feedback resistor. A smaller feedback resistor
will produce a wider bandwidth response. However, if the feed-
back resistance becomes too small, the gain flatness can be
affected. As a practical consideration, the minimum value of
feedback resistance for the AD8072/AD8073 was found to be
649 Ω. For resistances below this value, the gain flatness will be
affected and more significant lot-to-lot variations in device per-
formance will be noticed. Figure 5 shows a plot of the frequency
response of an AD8072/AD8073 at a gain of two with both feed-
back and gain resistors equal to 649 Ω.
6.1
6.0
5.9
5.8
5.7
5.6
5.5
5.4
0.1
V
A
R
V
S
O
V
L
=
= 2
= 150
= 0.2V p-p
5V
1V
1
0.1 dB
R
FREQUENCY – MHz
F
DIV
= 2k
10
25ns
±
100
R
1 dB
F
V
V
DIV
IN
OUT
= 649
500
7
6
5
4
3
2
1
0
On the other hand, the bandwidth of a current feedback ampli-
fier can be decreased by increasing the feedback resistance. This
can sometimes be useful where it is desired to reduce the noise
bandwidth of a system. As a practical matter, the maximum
value of feedback resistor was found to be 2 kΩ. Figure 5 shows
the frequency response of an AD8072/AD8073 at a gain of two
with both feedback and gain resistors equal to 2 kΩ.
Capacitive Load Drive
When an op amp output drives a capacitive load, extra phase shift
due to the pole formed by the op amp’s output impedance and
the capacitor can cause peaking or even oscillation. The top trace
of Figure 6, R
the AD8072/AD8073 when driving a 50 pF capacitor as shown in
the schematic of Figure 7.
The amount of peaking can be significantly reduced by adding
a resistor in series with the capacitor. The lower trace of Figure 6
shows the same capacitor being driven with a 25 Ω resistor
in series with it. In general, the resistor value will have to be
experimentally determined, but 10 Ω to 50 Ω is a practical range
of values to experiment with for capacitive loads of up to a few
hundred pF.
V
IN
= 100mV p-p
S
= 0 Ω, shows the output of one of the amplifiers of
R
S
1k
= 0Ω
50mV
50
R
S
= 25Ω
1k
AD8072/AD8073
R
S
20ns
C
50pF
L
R
1k
L

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