Ultralow Distortion

Current Feedback Differential ADC Driver

ADA4927-1/ADA4927-2

Rev. 0

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FEATURES

Extremely low harmonic distortion

−105 dBc HD2 @ 10 MHz

−91 dBc HD2 @ 70 MHz

−87 dBc HD2 @ 100 MHz

−103 dBc HD3 @ 10 MHz

−98 dBc HD3 @ 70 MHz

−89 dBc HD3 @ 100 MHz

Better distortion at higher gains than VF amplifiers

Low input voltage noise: 1.4 nV/√Hz

High speed

−3 dB bandwidth of 2.3 GHz

0.1 dB gain flatness: 150 MHz

Slew rate: 5000 V/μs, 25% to 75%

Fast 0.1% settling time: 10 ns

Low input offset voltage: 0.3 mV typical

Externally adjustable gain

Stability and bandwidth controlled by feedback resistor

Differential-to-differential or single-ended-to-differential

operation

Adjustable output common-mode voltage

Wide supply operation: +5 V to ±5 V

APPLICATIONS

ADC drivers

Single-ended-to-differential converters

IF and baseband gain blocks

Differential buffers

Differential line drivers

GENERAL DESCRIPTION

The ADA4927 is a low noise, ultralow distortion, high speed,

current feedback differential amplifier that is an ideal choice for

driving high performance ADCs with resolutions up to 16 bits

from dc to 100 MHz. The output common-mode level can easily be

matched to the required ADC input common-mode levels. The

internal common-mode feedback loop provides exceptional output

balance and suppression of even-order distortion products.

Differential gain configurations are easily realized using an

external feedback network comprising four resistors. The

current feedback architecture provides loop gain that is nearly

independent of closed-loop gain, achieving wide bandwidth,

low distortion, and low noise at higher gains and lower power

consumption than comparable voltage feedback amplifiers.

The ADA4927 is fabricated using the Analog Devices, Inc., silicon-

germanium complementary bipolar process, enabling very low

levels of distortion with an input voltage noise of only 1.3 nV/√Hz.

FUNCTIONAL BLOCK DIAGRAMS

1

–FB

2

+IN

3

–IN

4

+FB

11 –OUT

12 PD

10 +OUT

ADA4927-1

Figure 1.

ADA4927-2

1

–IN1

2

+FB1

3

4

5

–FB2

6

+IN2

18 +OUT1

14 PD2

13 –OUT2

Figure 2.

–40

–50

–60

–70

–80

–90

–100

–110

–120

–130

1

10

100

1k

FREQUENCY (MHz)

G = 1

G = 10

G = 20

Figure 3. Spurious-Free Dynamic Range vs. Frequency at Various Gains

The low dc offset and excellent dynamic performance of the

ADA4927 make it well suited for a wide variety of data acquisition

and signal processing applications.

The ADA4927-1 is available in a Pb-free, 3 mm × 3 mm 16-lead

LFCSP, and the ADA4927-2 is available in a Pb-free, 4 mm × 4 mm

24-lead LFCSP. The pinouts are optimized to facilitate printed

circuit board (PCB) layout and to minimize distortion. They are

specified to operate over the −40°C to +105°C temperature range.