ADA4939-1_16 Datasheet, PDF (1/24 Pages) Analog Devices – Ultralow Distortion, Differential ADC Driver

Data Sheet
FEATURES
Extremely low harmonic distortion
−102 dBc HD2 at 10 MHz
−83 dBc HD2 at 70 MHz
−77 dBc HD2 at 100 MHz
−101 dBc HD3 at 10 MHz
−97 dBc HD3 at 70 MHz
−91 dBc HD3 at 100 MHz
Low input voltage noise: 2.3 nV/√Hz
High speed
−3 dB bandwidth of 1.4 GHz, G = 2
Slew rate: 6800 V/μs, 25% to 75%
Fast overdrive recovery of <1 ns
±0.5 mV typical offset voltage
Externally adjustable gain
Stable for differential gains ≥2
Differential-to-differential or single-ended-to-differential
operation
Adjustable output common-mode voltage
Single-supply operation: 3.3 V to 5 V
APPLICATIONS
ADC drivers
Single-ended-to-differential converters
IF and baseband gain blocks
Differential buffers
Line drivers
GENERAL DESCRIPTION
The ADA4939-1/ADA4939-2 are low noise, ultralow distortion,
high speed differential amplifiers. They are an ideal choice for
driving high performance ADCs with resolutions up to 16 bits
from dc to 100 MHz. The output common-mode voltage is user
adjustable by means of an internal common-mode feedback loop,
allowing the ADA4939-1/ADA4939-2 output to match the input
of the ADC. The internal feedback loop also provides exceptional
output balance as well as suppression of even-order harmonic
distortion products.
With the ADA4939-1/ADA4939-2, differential gain configurations
are easily realized with a simple external feedback network of four
resistors that determine the closed-loop gain of the amplifier.
The ADA4939-1/ADA4939-2 are fabricated using Analog Devices,
Inc., proprietary silicon-germanium (SiGe), complementary bipolar
process, enabling them to achieve very low levels of distortion with
an input voltage noise of only 2.3 nV/√Hz. The low dc offset and
excellent dynamic performance of the ADA4939-1/ADA4939-2
make them well suited for a wide variety of data acquisition and
signal processing applications.
Rev. A
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Ultralow Distortion,
Differential ADC Driver
ADA4939-1/ADA4939-2
FUNCTIONAL BLOCK DIAGRAMS
ADA4939-1
–FB 1
+IN 2
–IN 3
+FB 4
12 PD
11 –OUT
10 +OUT
9 V_OCM
Figure 1. ADA4939-1
–IN1 1
+FB1 2
+V_S1 3
+V_S1 4
–FB2 5
+IN2 6
ADA4939-2
18 +OUT1
17 VOCM1
16 –VS2
15 –VS2
14 PD2
13 –OUT2
Figure 2. ADA4939-2
The ADA4939-1 (single) is available in a 3 mm × 3 mm, 16-lead
LFCSP, and the ADA4939-2 (dual) is available in a 4 mm × 4 mm,
24-lead LFCSP. The pinouts are optimized to facilitate printed
circuit board (PCB) layout and minimize distortion. The
ADA4939-1/ADA4939-2 are specified to operate over the
−40°C to +105°C temperature range; both operate on supplies
between 3.3 V and 5 V.
–60
V_{OUT, dm} = 2V p-p
–65
HD2
–70
HD3
–75
–80
–85
–90
–95
–100
–105
–110
1
10
100
FREQUENCY (MHz)
Figure 3. Harmonic Distortion vs. Frequency
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