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Data Sheet
FEATURES
Extremely low harmonic distortion (HD) −112 dBc HD2 at 10 MHz −84 dBc HD2 at 70 MHz −77 dBc HD2 at 100 MHz −102 dBc HD3 at 10 MHz −91 dBc HD3 at 70 MHz −84 dBc HD3 at 100 MHz
Low input voltage noise: 2.2 nV/√Hz High speed
−3 dB bandwidth of 1.9 GHz, G = 1 Slew rate: 6000 V/μs, 25% to 75% Fast overdrive recovery of 1 ns 0.5 mV typical offset voltage Externally adjustable gain 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 ADA4937-1/ADA4937-2 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 adjustable level of the output common mode allows the ADA4937-1/ADA4937-2 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.
With the ADA4937-1/ADA4937-2, 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 ADA4937-1/ADA4937-2 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 2.2 nV/√Hz. The low dc offset and excellent dynamic performance of the ADA4937-1/ADA4937-2 make them well-suited for a wide variety of data acquisition and signal processing applications.
Rev. E
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Ultralow Distortion Differential ADC Driver ADA4937-1/ADA4937-2
FUNCTIONAL BLOCK DIAGRAMS
ADA4937-1
16 –VS 15 –VS 14 –VS 13 –VS
–FB 1 +IN 2 –IN 3 +FB 4
12 PD 11 –OUT 10 +OUT 9 VOCM
06591-001
+VS 5 +VS 6 +VS 7 +VS 8
Figure 1. ADA4937-1 ADA4937-2
24 +IN1 23 –FB1 22 –VS1 21 –VS1 20 PD1 19 –OUT1
–IN1 1 +FB1 2
+VS1 3 +VS1 4 –FB2 5
+IN2 6
18 +OUT1
17 VOCM1 16 –VS2 15 –VS2 14 PD2
13 –OUT2
–IN2 7 +FB2 8 +VS2 9 +VS2 10 VOCM2 11 +OUT2 12
06591-002
Figure 2. ADA4937-2
–55 HD2, VS = 5.0V
–60 HD3, VS = 5.0V
–65
HD2, VS = 3.3V HD3, VS = 3.3V
–70
DISTORTION (dBc)
–75
–80
–85
–90
–95
–100
–105
–110
06591-003
–115 1
10 FREQUENCY (MHz)
100
Figure 3. Harmonic Distortion vs. Frequency
The ADA4937-1/ADA4937-2.