Data Sheet
FEATURES
Extremely low harmonic distortion (HD)
−106 dBc HD2 @ 10 MHz
−82 dBc HD2 @ 50 MHz
−109 dBc HD3 @ 10 MHz
−82 dBc HD3 @ 50 MHz
Low input voltage noise: 2.6 nV/√Hz
High speed
−3 dB bandwidth of 1000 MHz, G = +1
Slew rate: 4700 V/μs
0.1 dB gain flatness to 150 MHz
Fast overdrive recovery of 4 ns
1 mV typical offset voltage
Externally adjustable gain
Differential-to-differential or single-ended-to-differential
operation
Adjustable output common-mode voltage
Wide supply voltage range: +5 V to ±5 V
Single or dual amplifier configuration available
Ultralow Distortion
Differential ADC Driver
ADA4938-1/ADA4938-2
FUNCTIONAL BLOCK DIAGRAMS
ADA4938-1
TOP VIEW
16
–V
S
15
–V
S
14
–V
S
–FB 1
+IN 2
–IN 3
+FB 4
13
–V
S
12 PD
11 –OUT
10 +OUT
9
V
OCM
06592-001
Figure 1.
ADA4938-1
Functional Block Diagram
ADA4938-2
TOP VIEW
+V
S
8
+V
S
7
+V
S
5
+V
S
6
23
–FB1
22
–V
S1
21
–V
S1
19
–OUT1
18
+OUT1
17
V
OCM1
16
–V
S2
15
–V
S2
14
PD2
13
–OUT2
24
+IN1
–IN1
1
+FB1
2
+V
S1
3
+V
S1
4
–FB2
5
+IN2
6
APPLICATIONS
ADC drivers
Single-ended-to-differential converters
IF and baseband gain blocks
Differential buffers
Line drivers
+V
S2
9
+V
S2
10
20
PD1
V
OCM2
11
+OUT2
12
+FB2
8
–IN2
7
Figure 2.
ADA4938-2
Functional Block Diagram
–50
–60
–70
–80
–90
–100
–110
–120
–130
G = +2,
G = +2,
G = +2,
G = +2,
V
O, dm
= 5V p-p
V
O, dm
= 3.2V p-p
V
O, dm
= 2V p-p
V
O, dm
= 1V p-p
GENERAL DESCRIPTION
The
ADA4938-1/ADA4938-2
are low noise, ultralow distortion,
high speed differential amplifiers. It is an ideal choice for
driving high performance ADCs with resolutions up to 16 bits
from dc to 27 MHz, or up to 12 bits from dc to 74 MHz. The
output common-mode voltage is adjustable over a wide range,
allowing the
ADA4938-1/ADA4938-2
to match the input of the
ADC. The internal common-mode feedback loop also provides
exceptional output balance as well as suppression of even-order
harmonic distortion products.
Full differential and single-ended-to-differential gain configurations
are easily realized with the
ADA4938-1/ADA4938-2.
A simple
external feedback network of four resistors determines the
closed-loop gain of the amplifier.
The
ADA4938-1/ADA4938-2
are fabricated using the Analog
Devices, Inc., proprietary third generation, high voltage XFCB
process, enabling it to achieve very low levels of distortion with
an input voltage noise of only 2.6 nV/√Hz. The low dc offset and
excellent dynamic performance of the
ADA4938-1/ADA4938-2
Rev. B
Document Feedback
SFDR (dBc)
06592-202
1
10
FREQUENCY (MHz)
100
Figure 3. SFDR vs. Frequency and Output Voltage
makes them well-suited for a wide variety of data acquisition and
signal processing applications.
The
ADA4938-1
(single amplifier) is available in a Pb-free,
3 mm × 3 mm, 16-lead LFCSP. The
ADA4938-2
(dual
amplifier) is available in a Pb-free, 4 mm × 4 mm, 24-lead
LFCSP. The pinouts have been optimized to facilitate layout and
minimize distortion. The devices are specified to operate over
the extended industrial temperature range of −40°C to +85°C.
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2007–2016 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
06592-002
ADA4938-1/ADA4938-2
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagrams ............................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Dual-Supply Operation ............................................................... 3
Single-Supply Operation ............................................................. 5
Absolute Maximum Ratings............................................................ 7
Thermal Resistance ...................................................................... 7
ESD Caution .................................................................................. 7
Pin Configurations and Function Descriptions ........................... 8
Typical Performance Characteristics ............................................. 9
Test Circuts ...................................................................................... 17
Terminology .................................................................................... 18
Data Sheet
Theory of Operation ...................................................................... 19
Analyzing an Application Circuit ............................................ 19
Setting the Closed-Loop Gain .................................................. 19
Estimating the Output Noise Voltage ...................................... 19
The Impact of Mismatches in the Feedback Networks ......... 20
Calculating the Input Impedance of an Application Circuit ..... 20
Input Common-Mode Voltage Range in Single-Supply
Applications ................................................................................ 20
Terminating a Single-Ended Input .......................................... 21
Setting the Output Common-Mode Voltage .......................... 21
Layout, Grounding, and Bypassing .............................................. 23
High Performance ADC Driving ................................................. 24
Outline Dimensions ....................................................................... 25
Ordering Guide .......................................................................... 25
REVISION HISTORY
6/2016—Rev.
A to Rev. B
Changed CP-16-2 to CP-16-21, CP-24-1 to CP-24-10.. Throughout
Changed ADA4938-x to ADA4938-1/ADA4938-2 .. Throughout
Changes to Figure 1 and Figure 2 ................................................... 1
Changes to Figure 5 and Figure 6 ................................................... 8
Updated Outline Dimensions ....................................................... 25
Changes to Ordering Guide .......................................................... 25
10/2009—Rev. 0 to Rev. A
Added Settling Time Parameter, Table 1 ....................................... 3
Changes to Linear Output Current Parameter, Table 1 ............... 3
Added Settling Time Parameter, Table 3 ........................................5
Changes to Linear Output Current Parameter, Table 3 ................5
Changes to Figure 5 and Figure 6 ....................................................8
Added EP Row to Table 7 and EP Row to Table 8 ........................8
Changes to Figure 41...................................................................... 14
Added New Figure 53, Renumbered Sequentially ..................... 16
Changes to Table 9.......................................................................... 19
Added Exposed Pad Notation to Outline Dimensions ............. 25
Changes to Ordering Guide .......................................................... 25
11/2007—Revision 0: Initial Version
Rev. B | Page 2 of 26
Data Sheet
SPECIFICATIONS
DUAL-SUPPLY OPERATION
ADA4938-1/ADA4938-2
T
A
= 25°C, +V
S
= 5 V, −V
S
= −5 V, V
OCM
= 0 V, R
T
= 61.9 Ω, R
G
= R
F
= 200 Ω, G = +1, R
L, dm
= 1 kΩ, unless otherwise noted.
All specifications refer to single-ended input and differential output, unless otherwise noted. For gains other than G = +1, values for R
F
and R
G
are shown in Table 11.
±D
IN
to ±OUT Performance
Table 1.
Parameter
DYNAMIC PERFORMANCE
−3 dB Small Signal Bandwidth
Bandwidth for 0.1 dB Flatness
Large Signal Bandwidth
Slew Rate
Settling Time
Overdrive Recovery Time
NOISE/HARMONIC PERFORMANCE
Second Harmonic
Third Harmonic
IMD
IP3
Input Voltage Noise
Noise Figure
Input Current Noise
Crosstalk (ADA4938-2)
INPUT CHARACTERISTICS
Offset Voltage
Input Bias Current
Input Resistance
Input Capacitance
Input Common-Mode Voltage
CMRR
OUTPUT CHARACTERISTICS
Output Voltage Swing
Linear Output Current
Output Balance Error
T
MIN
to T
MAX
variation
Differential
Common mode
Conditions
V
OUT
= 0.1 V p-p
V
OUT
= 2 V p-p
V
OUT
= 2 V p-p
V
OUT
= 2 V p-p
V
OUT
= 2 V p-p
V
IN
= 5 V to 0 V step, G = +2
V
OUT
= 2 V p-p, 10 MHz
V
OUT
= 2 V p-p, 50 MHz
V
OUT
= 2 V p-p, 10 MHz
V
OUT
= 2 V p-p, 50 MHz
f
1
= 30.0 MHz, f
2
= 30.1 MHz
f = 30 MHz, R
L, dm
= 100 Ω
f = 10 MHz
G = +4, f = 10 MHz
f = 10 MHz
f = 100 MHz
V
OS, dm
= V
OUT, dm
/2; V
DIN+
= V
DIN−
= 0 V
T
MIN
to T
MAX
variation
−18
Min
Typ
1000
150
800
4700
6.5
4
−106
−82
−109
−82
89
45
2.6
15.8
4.8
−85
1
±4
−13
−0.01
6
3
1
−V
S
+ 0.3 to +V
S
− 1.6
−75
−V
S
+ 1.2 to +V
S
− 1.2
±75
−60
4
Max
Unit
MHz
MHz
MHz
V/µs
ns
ns
dBc
dBc
dBc
dBc
dBc
dBm
nV/√Hz
dB
pA/√Hz
dB
mV
µV/°C
µA
µA/°C
MΩ
MΩ
pF
V
dB
V
mA
dB
∆V
OUT, dm
/∆V
IN, cm
; ∆V
IN, cm
= ±1 V, f = 1 MHz
Maximum ∆V
OUT
; single-ended output
Per amplifier, R
L, dm
= 20 Ω, f = 10 MHz
∆V
OUT, cm
/∆V
OUT, dm
; ∆V
OUT, dm
= 1 V; f = 10 MHz
Rev. B | Page 3 of 26
ADA4938-1/ADA4938-2
V
OCM
to ±OUT Performance
Table 2.
Parameter
V
OCM
DYNAMIC PERFORMANCE
−3 dB Bandwidth
Slew Rate
Input Voltage Noise (RTI)
V
OCM
INPUT CHARACTERISTICS
Input Voltage Range
Input Resistance
Input Offset Voltage
Input Bias Current
V
OCM
CMRR
Gain
POWER SUPPLY
Operating Range
Quiescent Current
Conditions
Min
Typ
230
1700
7.5
−V
S
+ 1.3 to +V
S
− 1.3
10
3
0.5
−81
1.00
Data Sheet
Max
Unit
MHz
V/µs
nV/√Hz
V
kΩ
mV
µA
dB
V/V
V
mA
µA/°C
mA
dB
V
V
µs
ns
µA
µA
V
IN
= −3.4 V to +3.4 V, 25% to 75%
V
OS, cm
= V
OUT, cm
; V
DIN+
= V
DIN−
= 0 V
∆V
OUT, dm
/∆V
OCM
; ∆V
OCM
= ±1 V
∆V
OUT, cm
/∆V
OCM
; ∆V
OCM
= ±1 V
0.95
4.5
1.05
11
40
3.0
Power Supply Rejection Ratio
POWER DOWN (PD)
PD Input Voltage
Turn-Off Time
Turn-On Time
PD Bias Current
Enabled
Disabled
OPERATING TEMPERATURE RANGE
Per amplifier
T
MIN
to T
MAX
variation
Powered down
∆V
OUT, dm
/∆V
S
; ∆V
S
= ±1 V
Powered down
Enabled
37
40
2.0
−80
≤2.5
≥3
1
200
1
−760
−40
PD = 5 V
PD = −5 V
+85
°C
Rev. B | Page 4 of 26
Data Sheet
SINGLE-SUPPLY OPERATION
ADA4938-1/ADA4938-2
T
A
= 25°C, +V
S
= 5 V, −V
S
= 0 V, V
OCM
= +V
S
/2, R
T
= 61.9 Ω, R
G
= R
F
= 200 Ω, G = +1, R
L, dm
= 1 kΩ, unless otherwise noted.
All specifications refer to single-ended input and differential output, unless otherwise noted. For gains other than G = 1, values for R
F
and
R
G
are shown in Table 11.
±D
IN
to ±OUT Performance
Table 3.
Parameter
DYNAMIC PERFORMANCE
−3 dB Small Signal Bandwidth
Bandwidth for 0.1 dB Flatness
Large Signal Bandwidth
Slew Rate
Settling Time
Overdrive Recovery Time
NOISE/HARMONIC PERFORMANCE
Second Harmonic
Third Harmonic
Input Voltage Noise
Noise Figure
Input Current Noise
Crosstalk (ADA4938-2)
INPUT CHARACTERISTICS
Offset Voltage
Input Bias Current
Input Resistance
Input Capacitance
Input Common-Mode Voltage
CMRR
OUTPUT CHARACTERISTICS
Output Voltage Swing
Linear Output Current
Output Balance Error
T
MIN
to T
MAX
variation
Differential
Common mode
Conditions
V
OUT
= 0.1 V p-p
V
OUT
= 2 V p-p
V
OUT
= 2 V p-p
V
OUT
= 2 V p-p
V
OUT
= 2 V p-p
V
IN
= 2.5 V to 0 V step, G = +2
V
OUT
= 2 V p-p, 10 MHz
V
OUT
= 2 V p-p, 50 MHz
V
OUT
= 2 V p-p, 10 MHz
V
OUT
= 2 V p-p, 50 MHz
f = 10 MHz
G = +4, f = 10 MHz
f = 10 MHz
f = 100 MHz
V
OS, dm
= V
OUT, dm
/2; V
DIN+
= V
DIN−
= V
OCM
= 2.5 V
T
MIN
to T
MAX
variation
−18
Min
Typ
1000
150
750
3900
6.5
4
−110
−79
−100
−79
2.6
15.8
4.8
−85
1
±4
−13
−0.01
6
3
1
−V
S
+ 0.3 to +V
S
− 1.6
−80
−V
S
+ 1.2 to +V
S
− 1.2
±65
−60
4
Max
Unit
MHz
MHz
MHz
V/µs
ns
ns
dBc
dBc
dBc
dBc
nV/√Hz
dB
pA/√Hz
dB
mV
µV/°C
µA
µA/°C
MΩ
MΩ
pF
V
dB
V
mA
dB
∆V
OUT, dm
/∆V
IN, cm
; ∆V
IN, cm
= ±1 V
Maximum ∆V
OUT
; single-ended output
Per amplifier, R
L, dm
= 20 Ω, f = 10 MHz
∆V
OUT, cm
/∆V
OUT, dm
; ∆V
OUT, dm
= 1 V
Rev. B | Page 5 of 26
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