ADA4938-1_15 Datasheet, PDF (1/28 Pages) Analog Devices – Ultralow Distortion Differential ADC Driver

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-x is a low noise, ultralow distortion, high speed
differential amplifier. It is an ideal choice for driving high per-
formance 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 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-x. A simple external feedback
network of four resistors determines the closed-loop gain of the
amplifier.
The ADA4938-x is 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-x make it well-suited for a wide
variety of data acquisition and signal processing applications.
Rev. A
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Ultralow Distortion
Differential ADC Driver
ADA4938-1/ADA4938-2
FUNCTIONAL BLOCK DIAGRAMS
–FB 1
+IN 2
–IN 3
+FB 4
ADA4938-1
12 PD
11 –OUT
10 +OUT
9 V_OCM
Figure 1. ADA4938-1 Functional Block Diagram
–IN1 1
+FB1 2
+V_S1 3
+V_S1 4
–FB2 5
+IN2 6
ADA4938-2
18 +OUT1
17 V_OCM1
16 –V_S2
15 –VS2
14 PD2
13 –OUT2
Figure 2. ADA4938-2 Functional Block Diagram
–50
G = +2, V_{O, dm} = 5V p-p
G = +2, V_{O, dm} = 3.2V p-p
–60
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
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 parts are specified to operate over the
extended industrial temperature range of −40°C to +85°C.
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