ADA4938-1_16 Datasheet, PDF (1/26 Pages) Analog Devices – Ultralow Distortion Differential ADC Driver

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
APPLICATIONS
ADC drivers
Single-ended-to-differential converters
IF and baseband gain blocks
Differential buffers
Line drivers
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
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Ultralow Distortion
Differential ADC Driver
ADA4938-1/ADA4938-2
FUNCTIONAL BLOCK DIAGRAMS
ADA4938-1
TOP VIEW
–FB 1
+IN 2
–IN 3
+FB 4
12 PD
11 –OUT
10 +OUT
9 V_OCM
Figure 1. ADA4938-1 Functional Block Diagram
ADA4938-2
TOP VIEW
–IN1 1
+FB1 2
+V_S1 3
+V_S1 4
–FB2 5
+IN2 6
18 +OUT1
17 VOCM1
16 –V_S2
15 –V_S2
14 PD2
13 –OUT2
Figure 2. ADA4938-2 Functional Block Diagram
–50
G = +2, V_{O, dm} = 5V p-p
–60
G = +2, V_{O, dm} = 3.2V p-p
G = +2, V_{O, dm} = 2V p-p
G = +2, V_{O, dm} = 1V p-p
–70
–80
–90
–100
–110
–120
–130
1
10
100
FREQUENCY (MHz)
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.
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