AD9623 Ver la hoja de datos (PDF) - Analog Devices
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AD9623 Datasheet PDF : 6 Pages
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AD9623
+VS
6.8µF
+VS
6.8µF
0.1µF
0.1µF
RF RG
7
7
3
8
CB (OPTIONAL)
VIN
3
8
CB (OPTIONAL)
6
VOUT
6
VOUT
2
1
CF
2
1
CF
RF
RG
VIN
4
4
0.1µF
RF
0.1µF
RF
500Ω
RG
500 Ω
OBSOLETE CF
CI
VOUT
Figure 1. Transimpedance
Configuration
6.8µF
AV
=
–RF
RG
–VS
Figure 2. Inverting Gain Connection
Diagram
6.8µF
AV = 1+
RF
RG
–VS
Figure 3. Noninverting Gain Connection
Diagram
The CB capacitor (0.001 µF) connects to the internal high im-
pedance nodes of the amplifier. Using this capacitor will reduce
the large signal (4 V) step output settling time by 3 ns to 5 ns
for 0.05% or greater accuracy. For settling accuracy less than
0.05% or for smaller step sizes, its effect will be less apparent.
Under heavy slew conditions, this capacitor forces the internal
signal (initial step) amplitude to be controlled by the “on”
(slewed) transistor, preventing its complement from completely
Layout Considerations
As with all wide bandwidth components, printed circuit layout
is critical to obtain best dynamic performance with the AD9623.
The ground plane in the area of the amplifier and its associated
components should cover as much of the component side of the
board as possible (or first interior layer of a multilayer surface
mount board).
The ground plane should be removed in the area of the inputs
turning off. This allows for faster settling time of these (internal)
nodes and thus, the output also.
In the frequency domain, total (high frequency) distortion will
be approximately the same with or without CB. Typically, the
3rd harmonic will be greater than the 2nd without CB. This will
be reversed with CB in place.
and RF and RG to minimize stray capacitance at the input. The
same precaution should be used for CB, if used. Each power
supply trace should be decoupled close to the package with a
0.1 µF ceramic capacitor, plus a 6.8 µF tantalum nearby.
All lead lengths for input, output, and feedback resistor should
be kept as short as possible. All gain setting resistors should be
chosen for low values of parasitic capacitance and inductance,
APPLICATIONS
i.e., microwave resistors and/or carbon resistors.
The AD9623 is a voltage feedback amplifier and is well suited
for such applications as active filters, and log amplifiers. The
device’s wide bandwidth (270 MHz), phase margin (60°), low
noise current (2.6 pA /√Hz), and slew rate (2100 V/µs) give
higher performance capabilities to these applications over previ-
ous voltage feedback designs.
Microstrip techniques should be used for lead lengths in excess
of one inch. Sockets should be avoided if at all possible because
of their high series inductance. If sockets are necessary, indi-
vidual pin sockets such as AMP p/n 6-330808-3 should be used.
These contribute far less stray reactance than molded socket
assemblies.
Its settling time of 15 ns to 0.01% and 8 ns to 0.1%, and its low
harmonic distortion make it a good for choice for ADC signal
amplification. With superb linearity at relatively high signal fre-
An evaluation board is available from Analog Devices for a
nominal charge.
quencies, it is an ideal driver for ADCs up to 14 bits.
–4–
REV. 0
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