AD604ARZ Analog Devices Inc, AD604ARZ Datasheet - Page 15
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AD604ARZ
Manufacturer Part Number
AD604ARZ
Description
IC AMP VGA DUAL ULN 40MA 24SOIC
Manufacturer
Analog Devices Inc
Series
X-AMP®r
Type
Var Gain Ampr
Datasheet
1.AD604-EVALZ.pdf
(32 pages)
Specifications of AD604ARZ
Amplifier Type
Variable Gain
Number Of Circuits
2
Slew Rate
170 V/µs
-3db Bandwidth
40MHz
Current - Input Bias
400nA
Current - Supply
32mA
Current - Output / Channel
40mA
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
24-SOIC (7.5mm Width)
No. Of Amplifiers
2
Bandwidth
40MHz
Gain Accuracy
3dB
No. Of Channels
1
Amplifier Case Style
SOIC
No. Of Pins
24
Operating Temperature Range
-40°C To +85°C
Svhc
No SVHC (18-Jun-2010)
Package
RoHS Compliant
Number Of Channels
2
Number Of Elements
6
Power Supply Requirement
Dual
Common Mode Rejection Ratio
20dB
Voltage Gain Db
54dB
Input Resistance
0.3@±5VMohm
Input Bias Current
27000@±5VnA
Single Supply Voltage (typ)
Not RequiredV
Dual Supply Voltage (typ)
±5V
Power Dissipation
1.7W
Rail/rail I/o Type
No
Single Supply Voltage (min)
Not RequiredV
Single Supply Voltage (max)
Not RequiredV
Operating Temp Range
-40C to 85C
Operating Temperature Classification
Industrial
Mounting
Surface Mount
Pin Count
24
Package Type
SOIC W
Supply Voltage Range
± 5V
Rohs Compliant
Yes
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
For Use With
AD604-EVALZ - BOARD EVAL FOR AD604 AMP
Output Type
-
Voltage - Supply, Single/dual (±)
-
Gain Bandwidth Product
-
Voltage - Input Offset
-
Lead Free Status / Rohs Status
Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
AD604ARZ
Manufacturer:
Analog Devices Inc
Quantity:
135
Part Number:
AD604ARZ
Manufacturer:
ADI/亚德诺
Quantity:
20 000
Part Number:
AD604ARZ-RL
Manufacturer:
ADI/亚德诺
Quantity:
20 000
The larger portion of the input referred voltage noise comes
from the amplifier with 0.63 nV/√Hz. The current noise is
independent of gain and depends only on the bias current in
the input stage of the preamplifier, which is 3 pA/√Hz.
The preamplifier can drive 40 Ω (the nominal feedback resistors)
and the following 175 Ω ladder load of the DSX with low
distortion. For example, at 10 MHz and 1 V at the output, the
preamplifier has less than −45 dB of second and third harmonic
distortion when driven from a low (25 Ω) source resistance.
In applications that require more than 48 dB of gain range, two
AD604 channels can be cascaded. Because the preamplifier has
a limited input signal range and consumes over half (120 mW)
of the total power (220 mW), and its ultralow noise is not necessary
after the first AD604 channel, a shutdown mechanism that
disables only the preamplifier is provided. To shut down the
preamplifier, connect the COM1 pin and/or COM2 pin to the
positive supply; the DSX is unaffected. For additional details,
refer to the Applications Information section.
DIFFERENTIAL LADDER (ATTENUATOR)
The attenuator before the fixed-gain amplifier of the DSX is
realized by a differential 7-stage R-1.5R resistive ladder network
with an untrimmed input resistance of 175 Ω single-ended or
350 Ω differential. The signal applied at the input of the ladder
network is attenuated by 6.908 dB per tap; thus, the attenuation
at the first tap is 0 dB, at the second, 13.816 dB, and so on, all
the way to the last tap where the attenuation is 48.356 dB
(see Figure 41).
Figure 40. Shutdown of Preamplifiers Only
+DSXx
–DSXx
MID
10
11
12
NOTES
1. R = 96Ω
2. 1.5R = 144Ω
3
4
6
1
2
5
7
8
9
–DSX1
+DSX1
PAO1
FBK1
PAI1
COM1
COM2
PAI2
FBK2
PAO2
+DSX2
–DSX2
R
R
AD604
–6.908dB
1.5R
1.5R
VOCM
VNEG
VNEG
VGN1
GND1
VPOS
VPOS
GND2
VGN2
VREF
OUT1
OUT2
R
R
24
23
22
21
20
19
18
17
16
15
14
13
–13.82dB
1.5R
1.5R
R
R
Figure 41. R-1.5R Dual Ladder Network
–20.72dB
1.5R
1.5R
Rev. G | Page 15 of 32
R
R
–27.63dB
1.5R
1.5R
A unique circuit technique is used to interpolate continuously
among the tap points, thereby providing continuous attenuation
from 0 dB to −48.36 dB. The ladder network, together with the
interpolation mechanism, can be considered a voltage-controlled
potentiometer.
Because the DSX circuit uses a single voltage power supply, the
input biasing is provided by the VOCM buffer driving the MID
node (see Figure 41). Without internal biasing, the user would
have to dc bias the inputs externally. If not done carefully, the
biasing network can introduce additional noise and offsets. By
providing internal biasing, the user is relieved of this task and
only needs to ac-couple the signal into the DSX. Note that the
input to the DSX is still fully differential if driven differentially;
that is, Pin +DSXx and Pin −DSXx see the same signal but with
opposite polarity (see the Ultralow Noise, Differential Input-
Differential Output VGA section).
What changes is the load seen by the driver; it is 175 Ω when
each input is driven single-ended but 350 Ω when driven
differentially. This is easily explained by thinking of the ladder
network as two 175 Ω resistors connected back-to-back with
the middle node, MID, being biased by the VOCM buffer. A
differential signal applied between the +DSXx and −DSXx
nodes results in zero current into the MID node, but a single-
ended signal applied to either input, +DSXx or –DSXx, while
the other input is ac-grounded causes the current delivered by
the source to flow into the VOCM buffer via the MID node.
The ladder resistor value of 175 Ω provides the optimum
balance between the load driving capability of the preamplifier
and the noise contribution of the resistors. An advantage of the
X-AMP architecture is that the output referred noise is constant
vs. gain over most of the gain range. Figure 41 shows that the
tap resistance is equal for all taps after only a few taps away
from the inputs. The resistance seen looking into each tap is
54.4 Ω, which makes 0.95 nV/√Hz of Johnson noise spectral
density. Because there are two attenuators, the overall noise
contribution of the ladder network is √2 times 0.95 nV/√Hz
or 1.34 nV/√Hz, a large fraction of the total DSX noise. The
balance of the DSX circuit components contributes another
1.2 nV/√Hz, which together with the attenuator produces
1.8 nV/√Hz of total DSX input referred noise.
R
R
–34.54dB
1.5R
1.5R
R
R
–41.45dB
1.5R
1.5R
R
R
–48.36dB
1.5R
1.5R
175Ω
175Ω
AD604